NEWTON’S LAWS OF MOTION
NEWTON’S LAWS OF MOTION

Three Laws that Explain How and Why Objects
Move
NEWTON’S 1ST LAW OF MOTION

Law Of Inertia


Inertia Is An Object’s Resistance To Motion
An Object At Rest Stays At Rest, And An Object
In Motion Stays In Motion With The Same
Velocity, Unless Acted Upon By An Outside Force
NEWTON’S 1ST LAW EXAMPLES
1st Law (2:40)
NEWTON’S 2ND LAW OF MOTION

Acceleration is produced when a force acts on a mass.

The greater the mass (of the object being accelerated) the
greater the amount of force needed (to accelerate the object).

Heavier objects require more force to accelerate the same
amount as lighter objects.

The object accelerates in the direction that you push it

If you push the object with twice as much force, it accelerates
twice as much

If the object has twice the mass, it accelerates half as much
(with the same force)
NEWTON’S 2ND LAW EXAMPLES
2nd Law (3:10)
NEWTON’S LAWS REVIEW!

A space ship cruises through space with a constant
velocity without using any fuel.


A soccer player kicks a ball with her foot and her toes are
left stinging.


1st Law
Referred to as the law of inertia.


2nd Law
A picture is hanging on a wall and does not move.


3rd Law
A golf ball will accelerate faster and go farther than a
baseball if each are hit with the same amount of force.


1st Law
1st Law
A person’s body is thrown outward as a car rounds a
curve on a highway.

1st Law
3rd
2nd
1st
1st & 3rd
2nd
1st
3rd
3rd
2nd
3rd
1st
3rd
3rd
2nd
1st
3rd
2ND LAW FORMULAS AND UNITS

3 formulas
F=ma
 a=F/m
 m=F/a


Units

Newton
1 N = about the weight of a small apple (102 g)
 The amount of force necessary to accelerate one kilogram
1m/s2
 Mass: kg
 Acceleration: m/s2



∙
Force: kg m/s2 = N (Newtons)
You must have kg and m/s2 To do these problems!
Convert if you have to!
NEWTON’S 2ND LAW PROBLEMS!
1.
You give a shopping cart a shove down
the street. The cart is full of puppies and
has a mass of 18 kg. The cart accelerates
at a rate of 3 m/s2. How much force did
you exert on the cart?




2.
F = ma
F = 18 kg ∙ 3 m/s2
F = 54 kg ∙ m/s2
F = 54 N
You are super angry and throw a Barbie®
Doll across the room with a force of 2N
and it accelerates at 8 m/s2. What is the
mass of the doll in grams?
𝑓

M= 𝑎

M= 8 𝑚/𝑠2

M=
2𝑁
2𝑘𝑔 ∙ 𝑚/𝑠2
8 𝑚/𝑠2
1
kg or 0.25
4
M=
 M= 250 g

kg
3.
Last weekend, you decided to wander through the
mountains. You come across a pack of sleeping
coyotes. You decide to prank the largest coyote by
yelling into its ear and running off. Behind you, you
see the 30kg coyote chasing you as it exerts a force
of 120 N. What is its acceleration?

𝑓
A= 𝑚
120N
30kg
120kg∙m/s2
 A=
30kg
 A= 4 m/s2

A=
2ND LAW CALCULATIONS: YOUR TURN!


A 10 kg bowling ball would require what force to
accelerate it down an alley at a rate of 3.5 m/s2?
 F = ma
 F = 10kg ∙ 3.5 m/s2
 F = 35 kg ∙ m/s2
 F = 35 N
What is the mass of a truck if it produces a force
of 14,000 N while accelerating at a rate of 5 m/s2?
𝐹
𝑎
14,000 𝑁
5 𝑚/𝑠2
14,000 𝑘𝑔 ∙ 𝑚/𝑠2
5 𝑚/𝑠2

m=

m=

m=

m = 2,800 kg
NEWTON’S 3RD LAW OF MOTION
For Every Action There is an Equal and Opposite
Reaction
 Forces Act in Pairs

NEWTON’S 3RD LAW EXAMPLES

The rocket's action is to push down on the
ground with the force of its powerful
engines, and the reaction is that the ground
pushes the rocket upwards with an equal
force.
3rd Law (2:50)
MORE VIDEOS
All Laws (4:30)
 All Laws 2 (4:19)
 All Laws 3 (3:40)
