Force & Motion Unit

Energy-the ability to do work or cause change
Kinetic-energy of motion (like inertia, the more
mass and speed means more kinetic energy)
Potential-stored energy of position
1. Gravitational-the higher up, the more
2. Elastic-the more stretched or squeezed,
the more energy
Gravity-the force or pull one object has on another
(objects with more mass have more of a pull)
Earth is 6 times the mass of the moon, so Earth has
6 times the gravitational pull
So, if you weigh 120 pounds on Earth, you would
weigh 1/6th (20 pounds) on the moon
In space, far away from any planet, you weigh
nothing because no planet is pulling on you
What’s the difference between weight and mass?
Mass is a measure of how much matter an object
has (this does not change)
Weight is mass times the gravity acting on an object
(this changes based upon the mass of the planet or
moon you are near)
Speed = Distance ÷ Time
Example: What is the average speed of a
car that travels 400 km in 5 hours?
S = 400 ÷ 5 = 80 km/hr
Velocity is the speed and direction of an object
Acceleration is a change in velocity (speed or direction)
Acceleration = (final speed – initial speed) ÷ time
Example: Find the acceleration of a ball rolling
down a ramp whose speed increases from 0.5 m/s to
1.7 m/s in 10 seconds.
A = (1.7 – 0.5) ÷ 10 = 1.2 ÷ 10 = 0.12 m/s²
This means that every second, the ball travels
0.12 m/s faster than the previous second.
Newton’s 1st Law of Motion-an object remains at rest
or in motion unless acted on by a force
Inertia-the tendency of an object to resist changes in
*The more mass an object has, the more inertia it
*The more speed , the more inertia
Momentum-when an object is in motion, it has
*The greater the mass, the greater the momentum.
*The faster an object is moving, the greater the
Newton’s 2nd Law of Motion
Force = Mass x
Example: How much force does it take to accelerate
a 7 kg wagon at 3m/s²?
F = M x A, F = 7 x 3 = 21 Newtons (N)
Newton’s 3rd Law of Motion-For every action there is
an equal and opposite reaction.
1. A fish pushes its fins against water and the
water pushes back, so the fish moves forward
2. A water hose moves backward as water goes
out of hose
3. A bullet comes out of a gun and the gun kicks
Balanced Forces-act against each other (no
Unbalanced Forces-cause an object to move
Net Force-the total force acting on an object
**If Jane pushes a wagon East with a force of 70
Newtons and Dave pushes it West with a force of 50
Newtons, what is the net force?
70 – 50 = 20 Newtons East (the forces are
*Thermal energy (HEAT) always travels from warmer
objects to cooler objects
*Thermal energy lost by a warm object equals
the energy gained by the cool object it is in
contact with
Thermal equilibrium-when 2 objects are in
contact, they will eventually be the same
Convection-transfer of heat through a moving fluid,
warm air rises because it is less dense (liquids
or gases)
Conduction-transfer of heat through a substance
(metals are good conductors)
Radiation-transfer of heat through rays or waves
(sun’s rays)
Electric Force-between 2 objects with charges(+ or -)
An atom has 3 parts:
1. Proton-positively charged (+)
2. Electron-negatively charged (-)
3. Neutron-no charge (0)
An atom with a charge is called an ion.
If an atom loses an electron, it will have more
protons than electrons and will have a (+) charge,
and vice versa.
If # electrons = # protons, the charge is neutral (0)
Like charges repel each other and opposite charges
attract each other.
(+) and (+) = repel
(-) and (-) = repel
(+) and (-) = attract
Conductor-allows electrons to flow through it freely,
metals are good conductors
Insulator-Do not allow; rubber, wood, glass
**The closer 2 charge are, the greater the electric
force between them. (Similar to gravity)
Magnetic Force-Magnets are attracted to iron and
have a North or South charge.
N repels N
S repels S
N attracts S
Magnetic force decreases with distance.
Electromagnetism-magnetism from electric charges
in motion.
So, electricity can make
Magnetism can
make electricity!!
*Thermal Energy is the sum of Kinetic & Potential
Energy of all atoms in an object
*Temperature is a measure of average Kinetic
Energy of an object’s particles
SI units-metric units used by scientists everywhere
(m, g, L)
Law of Universal Gravitation-any 2 objects that have
mass are attracted to each other