1. Warm Up – Copy these definitions down in your notebook
Warm Up – Copy these definitions down in your notebook. Leave space in between each one for more notes.
An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object.
For every action, there is an equal and opposite reaction.

2. Newton’s Laws of Motion & Forces

3. Regarding Motion, Newton says:
“In order to move an object with mass,
you need to apply a force”
The greater the mass = The greater inertia => more force is needed

4. Force
Force – push or pull and causes things to accelerate
1000 kg

5. Balanced vs. Unbalanced Forces
Balanced Forces – The net force on an object is zero so no acceleration in any direction
Unbalanced Forces – The net force on an object is greater than zero causing acceleration in a direction

6. First Law of Motion
Inertia – The tendency of an object to resist a change in motion; resist a push/pull (force)
Newton’s 1st Law of Motion:
once in motion an object stays in motion - unless acted upon by an outside force
An object at rest stays at rest – unless acted upon by an outside force

7. Newton’s First Law and You
Because of inertia, objects (including you) resist changes in their motion. When the car going 80 m/hour is stopped by the brick wall, your body keeps moving at 80 m/hour.

8. Second Law of Motion Force = mass  acceleration (F = m  a)
Acceleration depends on the object’s mass and the force acting on the object
More Force = More Acceleration
More Mass = Less Acceleration

9. Second Law of Motion
If you apply more force to an object, it accelerates at a higher rate

10. Second Law of Motion
If the same force is applied to an object with greater mass, the object accelerates at a slower rate because mass adds inertia

11. Second Law of Motion

12. Third Law of Motion
For every action there is a reaction equal in magnitude but opposite in direction.
Upwards
motion
Downwards
force

13. Third Law of Motion

14. Balanced vs. Unbalanced Forces
Balanced Forces – The net force on an object is zero so no acceleration in any direction
Unbalanced Forces – The net force on an object is greater than zero causing acceleration in a direction

15. Take Notes on this Video

16. Forces will cancel each other and produce NO ACCELERATION!
Balanced Forces
Object
5 N
5 N
Equal Pushing
Forces will cancel each other and produce NO ACCELERATION!

17. Balanced Forces If these football players push
on each other equally as hard,
will either one move?

18. Balanced Forces
Gravity pulls down on you, the ground pushes back up, KEEPING YOU WHERE YOU ARE!

19. Forces will not cancel each other out and produce ACCELERATION!
Unbalanced Forces
Object
10 N
5 N
Not Equal Pushing
Forces will not cancel each other out and produce ACCELERATION!

20. What is the net force and in what direction?
Net Forces
Object
10 N
5 N
What is the net force and in what direction?
(10 N) – (5 N) = 5 N to the right

21. What is the net force and in what direction?
Net Forces
Object
20 N
5 N
What is the net force and in what direction?
(20 N) + (5 N) = 25 N to the right

22. What is the net force and in what direction?
Net Forces
Object
15 N
30 N
What is the net force and in what direction?
(30 N) – (15 N) = 15 N to the left

23. What is the net force and in what direction?
Net Forces
Object
10 N
10 N
What is the net force and in what direction?
(10 N) – (10 N) = 0 N

24. F m a Second Law of Motion
A car rolls down a ramp with a force of 2 newtons. The car has a mass of 0.5 kg. What is the acceleration of the car?
F = m  a
(2 N)  (0.5 kg) = 4 m/s2 F m a

25. and
Free Fall

26. Gravity
Gravity – g; acceleration caused by attraction between objects with mass
Gives weight
Causes free fall

27. Weight Fw = mg Weight – force caused by gravity’s pull measured in N
depends on mass, gravity, and location
weight is less on the moon due to less gravity
Weight
Gravity
Mass

28. Mass Mass (amount of matter) measured in kg
does NOT depend on gravity or location
mass is the same everywhere in the universe

29. Gravity on earth = 9.8 m/s2
Gravity on the moon = 1.6 m/s2
Fw = mg
The weight of 1 kg object ON EARTH
(1 kg)(9.8 m/s2) = 9.8 N
The weight of 1 kg object ON THE MOON
(1 kg)(1.6 m/s2) = 1.6 N

30. Practice
Unless the problem says otherwise, assume you are on Earth, where g = 9.8 m/s2
What is the weight of a 100 kg person?
(100 kg) x (9.8 m/s2) = 980 N
What is the mass of a rock that weighs 196 N?
(196 N) ÷ (9.8 m/s2) = 20 kg

31. What’s your weight on Mars?
Calculate and compare the weight of a 100 kg person on Earth and on Mars.
(g = 3.7 m/s2 on Mars)
Earth = (100 kg) × (9.8 m/s2) = 980 N
Mars = (100 kg) × (3.7 m/s2) = 370 N
The MASS did NOT change!!!

32. Free Fall
Free Fall – when gravitational pull is the only force acting on an object
Falling objects speed up 9.8 m/s2 for every second they fall
Time
Speed 1
9.8 2
19.6 3
29.4 4
39.2 5 49

33. Practice
The force of gravity on the surface of Mercury is much less than on Earth. A rock has a weight of 100 N on Earth. What do you know about the weight of the rock on Mercury?
The rock will weigh exactly 100 N
The rock will weigh more than 100 N
The rock will weigh less than 100 N
There is not enough information

34. Practice
A chair has a mass of 10 kilograms on Earth. What is the mass of the chair on Mercury?
Exactly 10 kg
More than 10 kg
Less than 10 kg
Not enough information

35. Practice
If an astronaut, with a mass of 90 kg, has a weight of N on the Moon, what is the value of the Moon’s gravitational acceleration? (145.8 N) ÷ (90 kg) = 1.62 m/s2