CIE A Levels Physics (9702)
CIE A Levels Physics (9702)
Grade Booster – AS – Frequently Examined
Questions (FEQs)
Measurements and Uncertainties
1. Define random errors. List possible causes of random errors in measurements.
•
Random errors are errors that occur due to unpredictable and uncontrollable fluctuations in
the measurement process.
•
Some possible causes of random errors in measurements are fluctuations in the environment,
variations in the operator's technique, variations in instrument readings due to thermal noise,
and limitations in the resolution of the measuring device.
2. Define systematic errors. List possible causes of systematic errors in measurements.
•
Systematic errors are errors that occur due to a consistent bias in the measurement process.
•
Possible causes of systematic errors in measurements include instrumental errors, calibration
errors, environmental effects, and errors in the method used to make the measurement.
3. Distinguish between systematic errors and random errors.
•
Systematic errors are caused by a consistent and repeatable bias in all readings, and are not
eliminated by averaging the measurements. To reduce systematic errors, it is necessary to
identify the source of the bias and correct it, either by changing the measurement method or
instrument or by subtracting the bias from all readings.
•
Random errors are caused by unpredictable factors that result in measurements that are
scattered around the true or mean value. These errors can be reduced by taking multiple
measurements and averaging the results to minimize the effect of the randomness.
4. Distinguish between scalar quantities and vector quantities.
•
Scalar quantities are physical quantities that can be described by a single value or number,
such as mass, temperature, and time.
•
Vector quantities are physical quantities that have both magnitude and direction, such as
displacement, velocity, and acceleration.
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CIE A Levels Physics (9702)
5. Define what is zero error. List possible causes of zero errors.
•
Zero error is a type of systematic error that occurs when a measuring instrument does not
read zero when it should. It can occur due to instrument defects or incorrect calibration and
can lead to inaccurate measurements.
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Kinematics
1. Define displacement.
•
Displacement can be defined as distance covered by an object from a fixed point in a specific
direction.
•
Displacement is a vector quantity that represents the change in position of an object in a
specific direction from a fixed reference point..
2. Explain the differences between the quantities distance and displacement.
•
Distance is a scalar quantity that refers to the total length of the path taken by an object during
its motion, regardless of direction.
•
Displacement, on the other hand, is a vector quantity that refers to the change in position of
an object in a given direction.
3. Explain how it is possible for a car to travel a certain distance and yet have zero
displacement.
A car can travel a certain distance and have zero displacement if it returns to its starting position.
4. Define velocity.
Velocity is a vector quantity that measures the rate of change of displacement with respect to
time.
5. Distinguish between speed and velocity.
6. Define acceleration.
Acceleration is a vector quantity that measures the rate of change of velocity with respect to time.
7. Describe, if any, by considering the forces acting on an object, the variation of acceleration
and velocity of an object falling in air.
•
When an object falls in air, it experiences two opposing forces: the gravitational force acting
downward and the air resistance force acting upward.
•
Initially, the object has zero velocity and experiences a net force in the downward direction,
causing it to accelerate downward.
•
As the object gains speed, the air resistance force increases until it balances the gravitational
force, resulting in a net force of zero and constant velocity, known as the terminal velocity.
•
At this point, the object no longer accelerates and falls at a constant speed.
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Dynamics
1. Define force.
Force is the rate of change of momentum.
2. What is meant by the weight of the object.
The weight of an object is the force exerted on it due to gravity.
3. State Newton’s first law of motion.
Newton’s first law of motion, states that an object at rest will remain at rest, and an object in motion
will continue to move in a straight line at a constant velocity unless acted upon by an external
force.
4. State Newton’s second law of motion.
Newton’s second law of motion states that the resultant force on a body is equal (or directly
proportional) to its rate of change of momentum.
Δ𝑝
Δ𝑡
Δ𝑝
Σ𝐹 =
Δ𝑡
Σ𝐹 ∝
5. Explain what is meant by equilibrium of a body.
Equilibrium of a body refers to a state where the net force acting on the object is zero, and it
remains at rest or moves with a constant velocity.
6. State two conditions necessary for an object to be in equilibrium.
•
the net force acting on the object is zero.
•
the net torque acting on the object is zero.
7. State what is meant by centre of gravity of an object.
The centre of gravity of an object is the point through which the total weight of the object can be
considered to act.
8. Define momentum.
Momentum is a physical quantity that describes the motion of an object and is equal to the product
of its mass and velocity.
9. State Newton’s third law of motion.
Newton's third law of motion states that when one body exerts a force on another body, the second
body simultaneously exerts a force on the first body that is equal in magnitude but opposite in
direction. These forces are of the same kind and act along the line joining the two bodies.
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10. State the principle of conservation of momentum.
The principle of conservation of momentum states that the total momentum of a system of objects
remains constant if there is no external force acting on the system.
11. State the relation between force and momentum.
Force is equal to rate of change of momentum.
𝐹=
Δ𝑝
Δ𝑡
12. State the difference between an elastic and an inelastic collision.
In an elastic collision, the total kinetic energy of the system is conserved, while in an inelastic
collision, some of the kinetic energy is lost and converted into other forms of energy, such as heat
or sound.
13. Define the moment of a force about a point.
The moment of a force about a point is the product of the force and the perpendicular distance
between the point and the line of action of the force.
14. State principle of moments.
The principle of moments states that for a body to be in equilibrium, the sum of the clockwise
moments about any point must be equal to the sum of the anticlockwise moments about the same
point.
15. A submarine descends vertically at constant velocity. Describe, with reference to the
forces acting on it, the relationship between their magnitudes.
When a submarine descends vertically at a constant velocity, the forces acting on it are in
equilibrium. Weight is balanced by the upthrust and the viscous drag.
16. Define the torque of a couple.
The torque of a couple is the product of one of the forces and the perpendicular distance between
the two forces.
17. Distinguish between the moment of a force and the torque of a couple.
•
The moment of a force is the product of the force and the perpendicular distance between the
pivot and the line of action of the force.
•
The torque of a couple is the product of one force and the perpendicular distance between
the two forces, where the forces are equal and opposite and not along the same line.
18. Define centre of gravity.
The centre of gravity is the point at which the entire weight of an object can be considered to act.
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Forces, Density, and Pressure
1. Define density.
Density is defined as the amount of mass per unit volume of a substance.
𝑚
𝜌=
𝑉
2. Define pressure.
Pressure is defined as the force exerted per unit area.
𝑝=
𝐹
𝐴
19. Distinguish between mass and weight.
Mass is a measure of the amount of matter in an object, while weight is the force exerted on an
object due to gravity and depends on the mass and the gravitational field strength.
3. An object, immersed in a liquid in a tank, experiences an upthrust. State what is the
physical reason for this upthrust.
The physical reason for the upthrust experienced by an object immersed in a liquid in a tank is
that the liquid exerts an upward force on the object due to the pressure difference between the
top and bottom of the object. This upward force is called upthurst and is equal to the weight of the
displaced liquid.
4. Explain the apparent loss in the weight of an object immersed in a liquid.
When an object is immersed in a liquid, it displaces some amount of liquid, which creates an
upward buoyant force on the object. This upward force reduces the apparent weight of the object,
making it seem lighter than it actually is.
Σ𝐹 = 𝑊𝑒𝑖𝑔ℎ𝑡 − 𝑈𝑝𝑡ℎ𝑟𝑢𝑠𝑡 − 𝑉𝑖𝑠𝑐𝑜𝑢𝑠 𝐷𝑟𝑎𝑔 = 𝑚𝑎
𝑎 = 𝑔′ =
𝑚𝑔 − 𝑈 − 𝑅
𝑚
5. State two situations where a body of constant mass may experience a change in its
apparent weight.
•
When the gravitational field is changed. For example, when it is taken to a different planet or
when it is taken to a different altitude on the same planet.
•
When it immersed in a liquid. The upward forces, upthrust and viscous drag will oppose
weight, causing a decrease in resultant force, thereby decreasing acceleration and apparent
weight.
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6. State the evidence for the molecules in solids and liquids having approximately the same
separation.
The similar density of liquids and solids indicates that their molecules have approximately the
same separation.
7. State the evidence for strong rigid forces between molecules in solids.
Solids' definite shape, volume, and incompressibility provide evidence for strong rigid forces
between molecules, keeping them tightly held in a fixed position with strong intermolecular forces.
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Work, Energy, and Power
1. Explain what is meant by work done.
•
Work done is defined as the product of force and displacement in the direction of the force.
•
Work is done when a force causes an object to move over a certain distance in the direction
of the force.
2. Define power.
Power is defined as the rate at which work is done or energy is transferred. It is the amount of
work done per unit time.
3. Define potential energy.
Potential energy is the energy that an object possesses due to its position or configuration, and it
is stored energy that can be converted into other forms of energy to do work.
4. Explain what is meant by gravitational potential energy and kinetic energy.
•
Gravitational potential energy is the energy of a mass due to its position in a gravitational field.
•
Kinetic energy, is the energy that an object possesses due to its motion (or velocity).
5. Distinguish between gravitational potential energy and elastic potential energy.
•
Gravitational potential energy is the energy of a mass due to its position in a gravitational field.
•
Elastic potential energy is energy stored in an object due to a force causing its deformation.
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Deformation of solids
1. State what is meant by elastic deformation.
Elastic deformation is the temporary deformation of a material in which the material returns to its
original shape and size once the external force is removed.
2. Explain what is meant by plastic deformation.
Plastic deformation is the permanent deformation of a material in which the material does not
return to its original shape and size once the external force is removed.
3. State Hooke’s law.
Hooke's law states that the extension of a spring is directly proportional to the force applied to it,
provided the limit of proportionality is not exceeded.
4. Describe the meaning of elastic limit.
The elastic limit is the point beyond which the deformation of a material becomes permanent, if
force is not removed before it.
5. Define tensile stress.
Tensile stress is the force acting per unit area perpendicular to the cross-sectional area of a
material when subjected to tensile force.
6. Define tensile strain.
Tensile strain is the change in length per unit length of a material when subjected to tensile force.
7. Define Young’s modulus.
Young's modulus is the ratio of tensile stress to tensile strain for a material within the elastic limit.
8. Suggest why the Young’s modulus is not used to describe the deformation of a liquid or a
gas.
Young's modulus is not used to describe the deformation of a liquid or a gas because these
materials do not exhibit a clear linear relationship between stress and strain within the elastic limit.
The deformation of liquids and gases is usually described in terms of their viscosity or fluidity.
9. What is the ultimate tensile stress of a material?
The ultimate tensile stress of a material is the maximum stress that it can withstand before it
breaks or fails.
10. Explain what is meant by strain energy (elastic potential energy).
Strain energy, or elastic potential energy, is the ability to do work that results from a change in
shape of an object, such as stretching, compressing, or twisting.
11. State whether copper is a ductile, brittle, or polymeric material.
Ductile
12. State whether glass is a ductile, brittle, or polymeric material.
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Brittle.
13. Describe a similarity and a difference between ductile and brittle materials.
•
Similarity: Both ductile and brittle materials exhibit elastic behavior and follow Hooke's law,
meaning they have an elastic region where they can deform and still return to their original
shape once the stress is removed.
•
Difference: Brittle materials have little or no plastic region, meaning they fracture or break
without significant deformation under stress, while ductile materials have a larger plastic
region, allowing them to deform significantly before they fracture or break.
14. Distinguish between the structure of a metal and a polymer.
•
Metals have a crystalline structure, with a regular arrangement of atoms and ions that allows
them to be malleable and ductile.
•
Polymers, have a long-chain molecular structure, which makes them flexible and easy to mold
into different shapes. Polymers can also be cross-linked to make them stronger and more
rigid.
15. With reference to arrangement of atoms, distinguish between metals, polymers, and
amorphous solids.
•
Metals are characterized by having a closely packed arrangement of atoms in a crystalline
lattice structure. This structure allows for the free movement of electrons, which is responsible
for many of the unique properties of metals such as conductivity and ductility.
•
Polymers, on the other hand, are made up of long chains of repeating molecular units. These
chains can be arranged in a variety of configurations, such as linear, branched, or crosslinked. Polymers can be either crystalline or amorphous, depending on the arrangement of
the chains.
•
Amorphous solids, also known as glasses, do not have a regular crystalline structure. Instead,
the atoms or molecules are arranged in a disordered fashion, similar to a liquid. This lack of a
regular structure gives rise to many unique properties of glasses, such as transparency and
brittleness.
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Waves
1. Define, for a wave, what is meant by its
a. Displacement
Distance of a point from its mean/equilibrium position.
b. Wavelength
Wavelength of a wave refers to the distance between two consecutive points in the wave
that are in phase.
2. State what is meant by a progressive wave.
A progressive wave is a wave that propagates or moves through a medium, carrying energy along
with it.
3. State what is meant by the frequency of a progressive wave.
The frequency of a progressive wave is the number of complete oscillations or cycles of the wave
that occur in one second.
4. State what is meant by the speed of a progressive wave.
The speed of a progressive wave is the rate at which the wave propagates through a medium. It
is equal to the product of the wavelength and the frequency of the wave.
5. State three distinct features of waves that are common to all regions of the electromagnetic
spectrum.
•
They are all transverse waves, and thus, can be polarized.
•
They can travel through a vacuum.
•
They obey the laws of reflection, refraction, diffraction, and interference.
•
They are electrically neutral, so unaffected by electric and magnetic fields.
•
They have oscillating electric and magnetic fields perpendicular to each other.
•
They can exhibit particulate behavior, i.e properties of particles, a phenomenon known as
wave-particle duality.
6. State one property of electromagnetic waves that is not common to other transverse
waves.
One property of electromagnetic waves that is not common to other transverse waves is that they
do not require a medium to propagate through.
7. State one difference and one similarity between longitudinal and transverse waves.
Difference: In longitudinal waves, the oscillation is parallel to the direction of wave propagation,
while in transverse waves, the oscillation is perpendicular to the direction of wave propagation.
Similarity: Both types of waves can undergo reflection, refraction, diffraction, and interference.
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8. By reference to vibrations of the points on a wave and to its direction of energy transfer,
distinguish between transverse waves and longitudinal waves.
Transverse waves are characterized by vibrations of the points in the medium perpendicular to
the direction of energy transfer, while longitudinal waves are characterized by vibrations of the
points in the medium parallel to the direction of energy transfer.
9. By reference to the direction of propagation of energy, explain what is meant by
polarization.
Polarization is the process of restricting the vibration of a transverse wave to one plane only,
perpendicular to the direction of wave propagation.
10. Describe what is meant by a polarized wave.
A polarized wave is a transverse wave that has been restricted to vibrate in only one plane.
11. State a characteristic property that is true for all transverse waves.
A characteristic property that is true for all transverse waves is that they exhibit polarization.
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Superposition
1. State what is meant by diffraction of a wave.
Diffraction of a wave refers to the bending of a wave around an obstacle or through an opening.
2. State what is meant by interference.
Interference is the combination of two or more waves that results in a new wave pattern with an
amplitude that is the sum of the individual waves.
3. Explain the meaning of coherence.
Coherence refers to the property of waves that have a constant phase relationship, which is
necessary for interference patterns to be formed.
4. State the principle of superposition.
The principle of superposition states that when two or more waves meet, the displacement of the
resulting wave is the sum of the displacements of the individual waves.
5. Use the principle of superposition to explain the formation of a stationary wave.
A stationary wave is formed by the superposition of two progressive waves of the same frequency
and amplitude, travelling in opposite directions. The waves interfere constructively and
destructively, producing regions of maximum and minimum amplitude, called nodes and
antinodes, respectively.
6. Describe, in terms of energy transfer, the difference between a progressive wave and a
stationary wave.
A progressive wave carries energy from one point to another, while a stationary wave does not
transfer energy. The energy of a stationary wave is contained within the oscillating particles of the
medium.
7. State two differences between progressive waves and stationary waves.
Progressive
Stationary
Transfer/propagate energy along the direction Do not transfer energy.
of propagation.
Amplitude is constant for all points.
Amplitude varies from max (at antinode) to
min/zero (at node). Particles between two
adjacent nodes have different amplitudes.
Adjacent particles vibrate out of phase
Adjacent particles between two successive
nodes vibrate in phase
All particles vibrate with the same frequency.
All particles oscillate at same frequency
except at nodes
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8. Explain the following terms used to describe stationary waves on a string.
a. Antinode
An antinode is a point on the string where the amplitude of the wave is maximum and the
displacement of the string is maximum.
b. Node
A node is a point on the string where the amplitude of the wave is zero and the
displacement of the string is also zero.
9. Explain why an interference pattern is observed on the screen in Young’s double slit
experiment.
An interference pattern is observed on the screen in Young's double slit experiment because the
waves passing through the two slits interfere with each other, creating regions of constructive and
destructive interference.
10. State three conditions required for maxima to be formed in an interference pattern
produced by two sources of microwaves.
•
The waves must be coherent.
•
The sources must be monochromatic.
•
The sources must be in phase.
11. State the effects, if any, on the fringes when the amplitude of the waves incident on the
double slits is increased.
Increasing the amplitude of the waves incident on the double slits will increase the
intensity/brightness of the fringes but will not affect their spacing.
12. State the effect, if any, on the appearance of the fringes observed on the screen when the
following changes are made, separately to a Young’s double slit arrangement.
a. The width of each slit is increased but the separation remains constant.
It will decrease the sharpness/contrast of the interference fringes.
b. The separation of the slits is increased.
It will increase the spacing between the fringes.
13. Describe the diffraction of monochromatic light as it passes through diffraction grating.
When monochromatic light passes through a diffraction grating, it is diffracted by the grating's
closely spaced slits and produces a series of bright fringes separated by dark regions. The bright
fringes correspond to constructive interference, while the dark regions correspond to destructive
interference.
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14. Coherent monochromatic light illuminates two narrow parallel slits and the interference
pattern that results is observed on a screen, some distance beyond the slits. Suggest a
change that could be made to increase the separation between the dark lines of the
interference pattern.
The distance between the slits should be decreased.
15. White light is incident on a diffraction grating. The diffraction pattern formed on the screen
has white light, called zero order, and colored spectra in other orders. Describe how the
principle of superposition is used to explain:
a. White light at the zero order
The white light observed at the zero order in a diffraction grating, which occurs because
all the colors of light are superimposed and add up to produce white light.
b. The difference in position of red and blue light in the first-order spectrum.
The difference in position of red and blue light in the first-order spectrum, which occurs
because red light has a longer wavelength and is diffracted at a larger angle than blue
light.
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Electricity and DC Circuits
1. Define charge.
•
Charge can be defined as product of current and time.
2. State what is meant by an electric current.
Electric current is the rate of flow of charged carriers, such as electrons, ions.
𝐼=
𝑄
𝑡
3. Define potential difference (p.d).
Potential difference (p.d) is the amount of energy transferred per unit charge as a charge moves
between two points in an electric circuit.
𝑉=
𝑊
𝑄
4. For a cell, explain the terms:
a. Electromotive force (e.m.f)
Electromotive force (e.m.f) is the electrical energy supplied by a source per unit charge.
b. Internal resistance
Internal resistance is the resistance within a cell or battery that reduces the output voltage
as a current is drawn from the cell.
5. Distinguish between electromotive force (e.m.f) and potential difference (p.d) in terms of
energy transformations.
•
Electromotive force (e.m.f) is the energy converted from chemical or other forms of energy
into electrical energy per unit charge.
•
Potential difference (p.d) is the energy converted from electrical energy to other forms of
energy per unit charge.
6. A cell with internal resistance supplies a current. Explain why the terminal potential
difference (p.d) is less than the electromotive force (e.m.f) of the cell.
The terminal potential difference (p.d) of a cell is less than its electromotive force (e.m.f) due to
the voltage drop across the internal resistance of the cell as current flows through it.
7. State the energy transformation that occurs in a
a. Battery
A battery converts chemical energy into electrical energy.
b. Resistors
A resistor converts electrical energy into heat energy.
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8. Define the resistance of a resistor.
Resistance is defined as the ratio of potential difference (p.d) to current (I) in a conductor.
9. Define the ohm.
The ohm is the SI unit of electrical resistance, defined as the resistance between two points in a
conductor when a constant potential difference of 1 volt produces a current of 1 ampere.
10. State Kirchhoff’s first law.
Kirchhoff's first law states that the total current entering a junction is equal to the total current
leaving the junction.
11. Kirchhoff’s first law is linked to the conservation of a certain quantity. State this quantity.
Kirchhoff's first law is linked to the conservation of charge, which states that the total charge in a
closed system remains constant over time.
12. State Kirchhoff’s second law.
Kirchhoff's second law states that the sum of electromotive forces (e.m.f.s) around any closed
loop in a circuit is equal to the sum of potential differences (p.d.s).
13. Kirchhoff’s second law is linked to the conservation of a certain quantity. State this
quantity.
Kirchhoff's second law is linked to the conservation of energy, which states that the total energy
in a closed system remains constant over time.
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Particle Physics
1. Explain the term isotopes.
Isotopes are atoms of the same element that have the same number of protons but different
numbers of neutrons in their nuclei.
2. State what is meant by
•
𝜶 – particle
Alpha (α) particle is a positively charged particle consisting of two protons and two
neutrons, identical to the nucleus of a helium atom.
•
𝜷 – particle
Beta (β) particle is an electron or positron emitted from the nucleus during radioactive
decay.
•
𝜸 – radiation
Gamma (γ) radiation is a type of electromagnetic radiation released during radioactive
decay, which has no mass or charge.
3. Describe the changes to proton number and the nucleon number of a nucleus when
emission occurs of
•
An 𝜶 – particle
When an alpha particle is emitted from a nucleus, the proton number decreases by 2 and the
nucleon number decreases by 4.
•
A 𝜷 – particle
When a beta particle is emitted, the proton number changes by 1, but the nucleon number
remains the same.
•
𝜸 – radiation
Gamma radiation does not change the proton or nucleon number of a nucleus.
4. Describe the two main results of the 𝜶 – particle scattering. Relate each of the results with
the conclusions that were made about the nature of atoms.
•
Most alpha particles were deviated through angles of less than 10°. This led to the conclusion
that atoms are mostly empty space.
•
A very small proportion of alpha particles was deviated through angles greater than 90°. This
suggested the existence of a small, dense, positively charged nucleus at the center of an
atom.
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5. The 𝜶 – particles in this experiment originated from the decay of a radioactive nuclide.
Suggest two reasons why 𝜷 – particles from a radioactive source would be inappropriate
for this type of scattering experiment.
•
Beta particles are much lighter than alpha particles and would be easily deflected by air
molecules and orbital electrons of gold atoms, making it difficult to obtain reliable data in the
scattering experiment.
•
Beta particles also have a greater range of energies than alpha particles, which could affect
the results of the experiment.
6. State the law of mass-energy conservation.
The law of mass-energy conservation states that the total mass-energy of a closed system
remains constant, although the mass and energy may be converted into each other.
7. Explain the meaning of spontaneous radioactive decay.
Spontaneous radioactive decay is the process by which an unstable atomic nucleus emits
particles or radiation to become more stable.
8. State the experimental observations that show radioactive decay is spontaneous.
Radioactive decay rate is constant over time and unaffected by external conditions.
9. Explain the meaning of random radioactive decay.
Random radioactive decay is the idea that the timing of radioactive decay events is unpredictable,
and each decay occurs independently of all others.
10. State the nature of a 𝜶 particle.
An alpha particle is a positively charged particle consisting of two protons and two neutrons,
identical to the nucleus of a helium atom.
11. State two properties of 𝜶 particles.
•
They have a low range of only a few centimeters.
•
They have low speeds, upto 10% of speed of light.
•
They have high ionization power.
•
They are positively charged and can be deflected in electric and magnetic fields.
12. State the nature of a 𝜷 particle.
A beta particle is an electron or positron emitted from the nucleus during radioactive decay.
13. State two properties of 𝜷 radiation.
•
They have high speeds, and can reach up to 99% of speed of light.
•
𝛽 − have moderate penetration power and can be stopped by few mm of Aluminium. 𝛽 + , on
the other hand, when collides with an electron, they annihilate, producing a high energy
gamma photon.
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•
𝛽 − have fair ionizing power, but 𝛽 + , have weak penetrative power, due to electron-positron
annihilation upon collision.
•
They can be easily deflected by electric and magnetic fields.
14. Nuclei do not contain 𝜷− particles. Explain the origin of the 𝜷− particle that is emitted from
nucleus during 𝜷− decay.
The 𝛽 − particle is formed when a neutron in the nucleus decays into a proton and an electron.
The electron is then emitted from the nucleus as a 𝛽 − particle.
15. Suggest why the 𝜷− particles are emitted with a range of different energies.
𝛽 − particles are emitted with a range of different energies because the energy released in the
decay is shared between the antineutrino and the 𝛽 − particle, and the momentum of the particles
can vary. This results in a range of possible energies for the 𝛽 − particle.
16. State what is meant by fundamental particle.
Fundamental particles are particles that are not made up of smaller particles.
17. State a similarity and a difference between an up quark and an up antiquark.
Difference: An up quark has a charge of +2/3e and an up antiquark has a charge of -2/3e.
Similarity: Both have the same mass.
18. Distinguish between mesons and baryons.
Mesons and baryons are both types of hadrons. Mesons are composed of a quark-antiquark pair,
while baryons are composed of three quarks.
19. A proton in a nucleus decays to form a neutron and a 𝜷+ particle.
a) State the name of another lepton that is produced in the decay.
(Electron) neutrino.
b) State the name of the interaction (force) that gives rise to this decay.
Weak Nuclear Force.
c) State which of the three particles (proton, neutron,or 𝜷+ ) has the largest charge to
mass ratio.
𝛽 + particle
d) State the quark composition of a proton.
Up-up-down (uud)
e) Use the quark model to show the the charge on a proton is +𝒆, where 𝒆 is the
elementary charge.
2
2
1
𝑒 + 𝑒 − 𝑒 = +𝑒
3
3
3
20
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