# Chapter 14 - Newton's Second & Third Law of Motion

## 17 terms · Lesson 2 - 2nd & 3rd law of Motion

### balanced forces

forces that cancel each other out when acting together on a single object

### unbalanced forces

forces that do not cancel each other out when acting together on a single object

### action

the force one object applies to a second. (Newton's 3rd law)

### reaction

the force with which an object responds to an action (Newton's 3rd law)

### work

the use of force to move an object a certain distance

### simple machine

a machine with few moving parts, making it easier to work

### lever

a simple machine made of a rigid bar a fixed point called a pivot point (or fulcrum)

### fulcrum

the pivot point of a lever

### effort arm

the part of the lever that applies force to the resistance arm

### resistance arm

the part of the lever that applies force to the load the machine acts against

### Newton's second Law of Motion

when an unbalanced force acts on an object, the objects acceleration equals the force divided by the objects mass. (action= force/mass)

### Newton's third Law of Motion

For every action the is a equal but opposite reaction .

### Example of Newton's 1st Law

a football will sit still on a level field until a kicker kicks it.
a ball will roll down a hill until the angle of the hill changes direction

### Example of Newton's 2nd law

when you use your arm to throw a football, the football excellerates through the air if the force of the throw is stronger than the mass and the air pushing against the ball.

### Example of Newton's 3rd law

Car moving forward: tires push on the road and the road pushes back - the reaction force propels the car forward.

### Two examples of inertia

When you are in a car moving forward and slam on the brakes, your body will move forward. If you go around a corner in a car really fast - your body will lean the opposite direction of the turn.

inclined plane
lever
pulley
screw
wedge
wheel & axle