1. Force and Motion Shopping Review
7th Grade Science

2. Formulas! Force = Mass x Acceleration --Measured in Newton's
Momentum = Mass x Velocity
--Measured in kilogram-meters per second (m/s)
Weight = Mass x Gravity
--Measured in Kilograms
Pressure = Force/Surface Area
--Measured in Newtons/kg

3. Forces Acting With or Upon Each Other
=25N (Net Force)
30N
30N
=60N (Net Force)
-These forces cancel each other out.
One Newton is the force required to move a one kilogram of mass 1 meter per second per second.

4. Friction
Friction is the force that one surface exerts on another when the two rub against each other.
Sliding friction- when solid surfaces slide across each other.
Rolling friction- when an object rolls over a surface.
Fluid friction- the friction that occurs when an object moves through a fluid.
Air Resistance- The fluid friction experienced by objects falling through air

5. Gravity & Free Fall
Gravity- is the force that pulls objects toward each other.
Free fall- when the only force acting on an object is gravity.
meters per second per second
o 1st second the velocity is 9.8 m/s
o 2nd second the velocity is 19.6 m/s
o 3rd second the velocity is 29.4 m/s…

6. Forces, Mass & Weight
Mass- Measure of the gravitational force which is Experienced by an object (like a rock) OR Produced by an object (such as a planet)
A Measure of matter in an object
Force- A push or a pull
Net force is the overall force on an object after all the forces acting on it are added.
Unbalanced forces will change an object’s motion.
Balanced forces will not change an object’s motion.
Weight- Measure of the force of gravity.

7. Newton's Laws of Physics
I. An object at rest stays at rest. An object in motion stays in motion at the same speed and direction, unless acted upon by an outside force.
II. The net force acting on an object is equal to the product of its acceleration and its mass.
(F= mass x acceleration)
III. If one object exerts a force on another object, then the second object exerts a force of equal strength in the opposite direction on the first object.
(Equal and Opposite Reactions)

8. Other Laws of Physics
Inertia (Law of Inertia): the tendency of an object to resist change in its motion, for example if a car stops, the objects in the car continue to move in the direction the car was moving.
Law of Universal Gravitation: states that any two objects in the universe will attract each other.
Gravitropism: The ability of a seedling to grow the stem upward and roots downward, no matter how the seed is placed in the soil.
Terminal velocity: The maximum velocity a falling object achieves (due to it’s Mass and Gravitational effect)

9. Basic Guidelines of Physics
As mass increases, inertia increases as well.
A snowball rolling downhill
As mass decreases, acceleration decreases as well.
As velocity moves in one direction, acceleration moves in the same direction.
Velocity and Acceleration move in tandem
The force of gravity increases when the mass of an object increases.
More mass of an object for gravity to attract.

10. To Increase Friction on a Roadway…
Add sand
Add salt
Bigger tires
Tap breaks often
Newer Tires
To Decrease Friction on a Roadway….
Smoother surface
Bald tires
Rain/water on road
Ice
No treads

11. Friction….
Sliding Friction: Solid surfaces SLIDE across each other
Both SLIDING and ROLLING friction: Involve surfaces, type of friction, measured in Newtons
ROLLING Friction: Rolls over a surface
Forces
Balanced forces: will change an object’s motion
Unbalanced forces: will not change an object’s motion
BOTH balanced and unbalanced forces are measured in Newtons using a SPRING SCALE.

12. Say WHAT?? As inertia increases, mass increases.
As mass increases, acceleration decreases.
As velocity moves in one direction, acceleration moves in the same direction.
The force of gravity increases when the mass of an object increases.