Download Study guide for Forces and Motion Test Chapter 2

Name_______________________________ period _________ date _____________
Study guide for Chapter 2 Test: Forces
Force
A push or pull, some are contact forces (pushing a cart) and others are
non-contact forces (electric force, magnetic force, gravity)
Newton
Abbreviation is N, the unit used to measure force, named after Isaac
Newton.
Net Force
The combination of all the forces acting on an object, the TOTAL force
on an object.
Balanced Forces (Explain what they are and what effect they have on an object’s
motion.)
When all the forces on an object cancel each other out.
 Balanced forces do NOT cause a change in motion.
 If an object was still, it stays still with balanced forces.
 If the object was moving and the forces become balanced, the
object keeps moving at a constant speed and direction.
Unbalanced Forces (Explain what they are and what effect they have on an object’s
motion)
When the forces on an object are unequal.
 Unbalanced forces DO cause a change in motion.
 Unbalanced forces cause an object to accelerate (speed up, slow
down, or change direction)
Name_______________________________ period _________ date _____________
Terminal velocity (Explain what it is and what has to happen to the forces on an
object to obtain terminal velocity)
The top speed an object reaches when being pulled downward by
gravity. It occurs when gravity and air resistance (fluid friction) equal
each other. When terminal velocity is reached, acceleration is at zero.
Inertia
The tendency (habit) of matter to resista a change of motion. It takes an
unbalanced force to cause an object to change its motion and overcome
inertia. An example would be when your car suddenly stops, your body
moves forward until your seatbelt stops you.
Friction (Explain what it is, why it happens, and how to increase or reduce friction)
The force that opposes or resists motion.
It occurs because surfaces are never completely smooth and the
surfaces “catch” on each other.

One thing that affects friction is force between objects and as it
increases, friction increases.

Another factor that influences friction is surface area, and as it
increases, friction increases.

The third factor that influences friction is surface substance, and as
it increases (or gets rougher), friction increases.
Four types of friction and examples:
Static: When an object is resisting motion, and not yet moving.
Name_______________________________ period _________ date _____________
 Ex. Pushing a heavy piece of furniture.
Sliding: When 2 solids slide past each other.
 Ex. Sliding down a slide at the playground, erasing
pencil marks.
Rolling: When one of the objects is round
 Ex. Wheels of any type, rollers in a factory, ball
bearings
Fluid: (Make sure you know that both liquids and gases are fluids.)
When one of the substances is a fluid.
 Ex. Swimming, air resistance when biking
The two factors that affect gravity and how they affect gravity:

One thing that affects gravity is distance and as it increases, gravity
decreases.

The other factor that influences gravity is mass , and as it increases,
gravity increases.
Newton’s 3 Laws of Motion (Define and be able to apply all three laws to real life
events.)
1st law: An object in motion will stay in motion and an object at rest
will stay at rest until acted upon by an unbalanced force. It takes
an unbalanced force to overcome inertia and make an object
accelerate (speed up, slow down, change direction)
2nd law: The acceleration of an object depends on the force applied
to the object and the mass of the object.
Name_______________________________ period _________ date _____________
 If the mass of an object increased, but the force on it stayed
constant then the acceleration of the object would decrease.
o Ex: If a car and truck were racing but both have
the same engine, the car will have more
acceleration and win.

If the force on an object increased, but the mass of the object
stayed the same then the acceleration would increase.
o Ex. If I push my sister on the swings soft vs.
hard, the stronger push will accelerate her
more.

If the mass doubled and the force was cut in half, then the
acceleration would be reduced to ¼
o Example: If I push a cart filled with 2x the
groceries, but have a child (smaller, weaker)
push it with ½ my force and the cart will
accelerate only ¼ as much.
3rd law: For every action there is an equal and opposite reaction.
***Action/Reaction forces do NOT act on the same object. They
are not balanced forces, because they act on separate objects.***

If an action force was wind pushing/pulling on a windmill

The reaction force would be the windmill pushing/pulling on the wind (air
molecules)

The result of the action force would be: The windmill starts to turn

The result of the reaction force would be: The air molecules slow down when
they hit the windmill.