Physics Exam 1
Forces
Constant force: when objects are physically touching each other ( friction, tension,
normal force)
Friction
- Can be expressed in newtons or pouds
● Resists the motion of two surfaces sliding past each other
1) Static Friction: the force that keeps an object at rest
2) kinetic/dynamic friction: occurs when an object is already in motion, usually less
than static friction meaning it is easier to keep and object moving once it has
already started moving
3) Rolling friction: this is the force that resists the motion of rolling objects (wheels) it
is typically much smaller than static of kinetic friction.
● Surface roughness tends to create more friction because of the interlocking of
surface irregularities.
● Different materials have different coefficients of friction which determines if much
friction will occur between the two surfaces.
Tension
● Direction: tension always acts along the length of the rope or string. Tension
force is always directed aways from the object being pulled
● Magnitude: the magnitude of tension can vary. It is usually the same throughout
an ideal, massless rope if the rope is not accelerating.
● Tension has both magnitude and direction.
How it works
- Equilibrium: If an object is hanging from a rope and is at rest, the tension in the
rope is equal to the weight of the object (the gravitational force acting on it).
- Acceleration: If the object is accelerating, the tension will be greater than the
weight of the object.
Gravitational Force
● The attraction between two masses; it pulls objects toward one another. The
more massive an object is, the stronger its gravitational pull, and the farther apart
two objects are, the weaker the gravitational force between them
Electromagnetic Force
● Acts between charged particles, responsible for electricity and magnetism.
- Attractive force: Between opposite charges (e.g., protons and electrons).
- Repulsive force: Between like charges (e.g., two electrons or two protons).
1) v=s/t
v: Average velocity (or speed) of the object, typically measured in meters per second (m/s).
s: Total distance traveled by the object, measured in meters (m).
t: Total time taken to travel that distance, measured in seconds (s).
2) 𝑎= Δ𝑣/𝑡
a: Acceleration, which measures how quickly an object's velocity changes, typically expressed in meters
per second squared (m/s²).
Δv: Change in velocity, which is the difference between the final velocity (vf) and the initial velocity (vi). It
can be expressed as Δv=vf−vi\t
t: Time over which the change in velocity occurs, measured in seconds (s).
3) d=(1/2​)gt^2
d: The distance fallen, typically measured in meters (m).
g: The acceleration due to gravity, which is approximately 10 m/s near the Earth's surface.
t: The time the object has been falling, measured in seconds (s).
4) ∑𝑭=ma
∑F: net force acting on the object. Vector sum of all forces
m: mass of the object (kg)
a: the acceleration of the object, measured in meters per second squared (m/s²)
5) w=mg
W: Weight of the object, typically measured in newtons (N).
m: Mass of the object, measured in kilograms (kg).
g: Acceleration due to gravity, which is approximately 10 m/s near the surface of the Earth.
6) W=Fd
W: Work done, measured in joules (J).
F: Force applied, measured in newtons (N).
d: Distance over which the force is applied, measured in meters (m).
7) W=ΔE
W: Work done on or by a system, measured in joules (J).
ΔE: Change in energy of the system, also measured in joules (J).
8) K=1/2mv^2
K: Kinetic energy, measured in joules (J).
m: Mass of the object, measured in kilograms (kg).
v: Velocity of the object, measured in meters per second (m/s).
9) PE=mgh
PE: Gravitational potential energy, measured in joules (J).
m: Mass of the object, measured in kilograms (kg).
g: Acceleration due to gravity, approximately10 m/s near the surface of the Earth.
h: Height of the object above a reference point, measured in meters (m).
10) E=K+PE
E: Total mechanical energy of the system, measured in joules (J).
K: Kinetic energy of the object, measured in joules (J).
PE: Gravitational potential energy of the object, measured in joules (J).
11) F= GMm/r^2
F: Gravitational force between the two masses, measured in newtons (N).
G: Universal gravitational constant, approximately 6.674×10−11 N m2/kg2
m1and m2​: The masses of the two objects, measured in kilograms (kg).
r: The distance between the centers of the two masses, measured in meters (m).
g= 10 m/s
G= 6.67 x 10^-11 N m^2 kg^-2
1 pound [as unit of mass]=0.45 Kg.
1 pound [as unit of force]=4.5 Newtons.