Physics Study Guide:

Force- A push or a push that results in a change in an objects speed, shape, motion, or direction.

Balanced Forces- Forces that are equal in size and opposite in direction, resulting in no change in motion.

1. At Rest 2. Constant Speed

Unbalanced Forces-A force that is not opposed by an equal and opposite force and therefor results in motion.

1. Change in the objects Acceleration=speed up, slow down, change directions

Newton’s 1st Law (Law of Inertia)-An object in motion stays in motion, and an object at rest stays at rest unless acted upon by an outside force. (SEATBELTS)

Inertia- The tendency of an object to resist changes in motion.

Mass is a measure of inertia.

-An object with a small mass has less inertia than an object that has a large mass.

-So, changing the motion of an object that has a small mass is easier than changing the motion of an object that has a large mass.

Newton’s 2nd Law (Law of Acceleration)-F = m x a. The greater the mass of an object, the more force needed to accelerate the object.

Newton’s 3rd Law (Law of Action-Reaction)-For every action there is an equal and opposite reaction.

Speed: How fast an object is moving (distance ÷ time) / Velocity: Speed + Direction / Acceleration-A change in speed of an object over time
The car traveled 20 mph / The car traveled 20 mph South / The car went from 20mph to 65 mph
The boy rode his bike 10m/min / The geese flew 10 m/hr North / The motorcycle slowed to a stop
The train went 45 km/hr / The car traveled on a curve / The roller coaster came down a hill

Mass- The amount of matter an object has.

Gravity- The natural force that attracts objects toward Earth or any other object that has mass

Friction-The force that resists movement which is caused by two objects rubbing against each other.

Law of Inertia
(1st Law) / Law of Acceleration
(2nd Law) / Law of Action-Reaction
(3rd Law)
A mail truck stops suddenly causing the basket of mail to fall forward onto the floor. / A dump truck and a race car speed up at different rates when the traffic light turns from red to green. / A rocket launching upward
A girl riding her bike slams on the breaks. The bike stops but she stays in motion going over the handle bars / It is harder to move a bowling ball than a marble. / A kayaker paddles the water backwards but the kayak goes forward
A pile of books won’t move until you pick them up / It is very difficult to move a box of books vs a box of pillows / The girl pushes down on the trampoline and then flies up.
Joe pushes 70 Newton’s to the right and Cade pushes 65 Newton’s to the left. What is the net force and direction that one of them will move?
70 - 65 =5 Newton’s Right.
(Opposite Subtract) / See examples on the back of word problems / A sling shot is flung in one direction and causes the rock to fly in the opposite direction.

Newton’s 2nd Law F= m x a Examples:

What force does Cindy need to produce in order to throw his 10 kg bowling ball down the alley with an acceleration rate of 3 m/s2?

F = m x a F=? F= 3 x 10

M=10 kg F= 30 N

A=3 m/s2

A force of 250 Newton’s is applied to an object that accelerates at a rate of 5 m/s2. What is the mass of the object?

F = m x a F=250 N 250= ? x 5

M=? 250/5=m

A=5 m/s2 m= 50 kg

What is the acceleration of a 50 kg object pushed with a force of 500 Newton’s?

F = m x a F=500 N 500= 50 x ?

M=50 500/50=m

A= ? a= 10 m/s2

Units of measurement:

Force= Newton’s (N)

Mass= Kilograms (kg)

Acceleration= m/s2