# Chapter 5 & 6: Motion, forces, friction, gravity

## 45 terms

a push or pull

move objects

no

### What is Newton's first law of motion (state it):

Object at rest will remain at rest, moving object will remain in motion

Law of inertia

### What is inertia?

tendency of an object to resist change in motion

### What does inertia depend on?

mass of an object

### What is friction?

force of one surface against another

### What does strength of friction depend on?

texture of the surfaces & how hard they are pushed together

### What is Newton's 2nd law of motion?

force=mass x acceleration

### What does Newtons second law mean in terms of changes in force and mass acceleration?

increase in force=increase in acceleration, increase in mass=decrease in acceleration

### What is Newton's third law of motion?

every action there is an equal and opposite reaction; forces always act in pairs

### What is gravity?

force of attraction between objects due to their masses

### What is freefall?

only force acting on an object is gravity

### What is acceleration?

the rate at which velocity changes over time

### What is the acceleration due to gravity? Explain.

Every second an object is falling its velocity increases by 9.8m/s. all objects free fall accelerate at the same rate.

### What is weight?

measure of the force of gravity on an object.

### What is mass?

measure of the amount of matter in that object.

### What is the Law of Universal Gravitation?

The force of gravity that acts between all objects in the universe, any two objects that attract each other.

### What does the strength of gravitational pull depend on?

mass and distance between two objects.

### How would you figure out your weight on the moon??

multiply by 1/6 of weight on earth

### motion

A change in position relative to a reference point, measured by distance and time

### Frame of Reference

The point from which movement is determined

### Speed

The distance traveled by moving objet per unit of time

### Average Speed

The speed of moving objects is not always constant

### Velocity

Speed in a given direction

### Acceleration

The rate of change in velocity

### Deceleration

Term used to mean a decrease in speed:negative acceleratrion

Any push or pull

### Friction

A force opposing motion

### Gravity

The force of attraction between all objects in the universe

### Free Fall

An object falling under the influence of gravity: no air resistance

### Weight

The effect of gravity on an object's mass

### Momentum

The product of the mass of an object and it's velocity

### Newton's third law

Explains why forces act in pairs:for every force there is an equal and opposite reaction force

50km/hr

100km/hr

10km/h

### Calculate the acceleration of a bicyclist traveling north that slows down from 15m/s to 5 m/s in 2 sec?

5m/sec deceleraton

<----15N

35N--->

### Balanced force

a force that will not cause an object to move

### Unbalanced Force

a force that causes an object to move

### Newton

unit used to measure force

### Net force

Combination of all forces acting on an object