2. THE LAW OF
Newton’s 1st Law
INERTIA

3. Newton’s 1st Law of Motion
After the ball is kicked, what forces are acting on it while it rolls?
What if we could remove those forces? What would happen then if we kicked the ball?
GRAVITY
Friction

4. Newton’s 1st Law of Motion
Newton’s 1st law of motion states:
An object at rest will remain at rest,
-and-
an object moving at a constant velocity will continue moving at a constant velocity,
-UNLESS-
it is acted upon by an unbalanced force.

5. Newton’s 1st Law of Motion
BASICALLY…
Objects resist any change to their motion!
This resistance is called INERTIA.
Which one would be easier to push?
or…
That’s because larger objects have more inertia (more resistance to a change in their motion)!

6. Newton’s 1st Law of Motion
Unfortunately, your bed really doesn’t make itself…
And dirty clothes won’t pick themselves up off the floor!
That’s because things at rest will stay at rest until an unbalanced force (like your arms lifting the sheets) acts on them.
Make your bed!
Do the laundry!

7. Newton’s 1st Law of Motion
What would happen to the things inside the car if the car hit a wall?
That’s because things moving at a constant velocity will stay at a constant velocity unless acted upon by an unbalanced force.
The car was acted upon by an outside force – the force of the wall hitting the car.
The person inside the car wasn’t hit by the force of the wall, so he kept moving at the same speed and in the same direction.
Inside a moving vehicle, everything is moving at the same velocity – your body, the objects in the car, and the car itself.

8. Newton’s 1st Law of Motion
Explain this animation:
The truck is stopped by the force of the impact with the car, but the ladder continues to move at its original speed and in its original direction because of inertia.

9. Newton’s 1st Law of Motion
So, how did the tablecloth demo work?
The cloth experienced a pulling force that caused it to start moving. The dishes did not have a direct force applied to them, so they remained in their places because of inertia.

10. Newton’s 1st Law of Motion
Following the instructions on your sheet, do each of the activities at your desk.
In your notebook, write the title of each activity and explain in at least two complete sentences how it works, using Newton’s 1st Law.

11. Newton’s Laws of Motion Foldable 1) Label your foldable like the one shown on the right. 2) Cut along the 2 dotted lines to make flaps. 3) On the inside, write down what the law states. 4) Write down an example of a situation that shows the law in action.
NEWTON’S
L A W S
Newton’s First Law of Motion
Newton’s Second Law of Motion
Newton’s Third Law of Motion

12. THE LAW OF
Newton’s 2nd Law
Acceleration

13. Let’s review Newton’s 1st Law
This law deals with situations where forces are balanced…
When forces are balanced, objects resist any changes in their motion… that’s called INERTIA.

14. Newton’s 1st Law of Motion
If no one kicks the ball, what will happen?
Objects at rest will remain at rest…

15. Newton’s 1st Law of Motion
If there was NO FRICTION (no unbalanced force) to slow down the ball, what would happen?
Objects in motion will remain in motion …

16. Newton’s 1st Law of Motion
The ladder’s inertia keeps it moving forward after the unbalanced force (car) stops the truck…

17. Newton’s 2nd Law of Motion
Newton’s 2nd law of motion describes how UNBALANCED FORCES and MASS affect the ACCELERATION of an object.
Let’s try it!

18. Test 1 – Increasing Force
Small Force - Blow through the straw lightly toward the marble. Observe the marble’s motion.
Large Force – Blow the straw with more force toward the marble. Observe the marble’s motion.
How does increasing the force affect the marble’s acceleration?

19. Test 2 – Increasing Mass
Small Mass (marble) - Blow through the straw as hard as you can. Observe the marble’s motion.
Large Mass (golf ball) – Blow the straw as hard as you can. Observe the golf ball’s motion.
How does increasing the mass affect the the object’s acceleration?

20. So, how do unbalanced forces affect an object’s motion?
How does a batter’s swing affect the acceleration of a baseball?
Homerun Hit
Sacrifice Bunt

21. So, how do unbalanced forces affect an object’s motion?
The harder you hit, the faster it goes!
The greater the force, the greater the acceleration…
Homerun Hit
Sacrifice Bunt

22. So, how does mass affect an object’s motion?
Which shopping cart would move faster with a single push?
Empty Cart
Full Cart

23. So, how does mass affect an object’s motion?
The fuller the cart, the slower it goes!
The more mass, the less acceleration…
Empty Cart
Full Cart

24. Newton’s 2nd Law of Motion
It states:
ACCELERATION depends on the object’s MASS, and the net FORCE acting on the object.
We can also write it mathematically:
Force = Mass x Acceleration

25. Newton’s 2nd Law Force = Mass x Acceleration M F A
If you want less acceleration with the same force, you must increase the mass.
If you lower the mass but keep force the same, acceleration will increase. M F A
If you raise the mass but keep force the same, acceleration will decrease.
If you want more acceleration with the same force, you must decrease the mass.

26. Newton’s 2nd Law Force = Mass x Acceleration
If you want less acceleration with the same mass, you must decrease the force.
If you want more acceleration with the same mass, you must increase the force.

27. Newton’s 2nd Law Force = Mass x Acceleration
If you lower the mass but want the same acceleration, you must decrease the force.
If you raise the mass but want the same acceleration, you must increase the force.

28. Newton’s 2nd Law of Motion
Force = Mass x Acceleration
Mr. Sawyer’s car ran out of gas. How much force does Mr. Sawyer need to push his 750kg car at an acceleration of 1 m/s2?
F = m x a
F = 750 kg x 1 m/s2
F = 750 N right
750 kg
1 m/s2

29. Try one on your own…
Ms. Litwak’s van runs out of gas. How much force does she need to push the 2000kg van at an acceleration of 0.5 m/s2?
0.5 m/s2
F = m x a
F = 2000 kg x 0.5 m/s2
F = 1000 N right

30. Newton’s 2nd Law of Motion
Speed, Distance & Time
We can also write the formula like this:
Acceleration = Force
Mass
Mass = Force
Acceleration
Force = Mass x Acceleration m F a

31. Newton’s 2nd Law of Motion
Find the golf ball’s acceleration.
The putter hits the 0.05 kg golfball with a force of 1 N.
The driver hits the 0.05 kg golfball with a force of 8 N.

32. Newton’s 2nd Law of Motion
Use Newton’s 2nd law of motion to explain in words the difference in the motion of the golf balls.

33. Newton’s Laws of Motion Foldable 1) Label your foldable like the one shown on the right. 2) Cut along the 2 dotted lines to make flaps. 3) On the inside, write down what the law states. 4) Write down an example of a situation that shows the law in action.
NEWTON’S
L A W S
Newton’s First Law of Motion
Newton’s Second Law of Motion
Newton’s Third Law of Motion

34. THE LAW OF
Newton’s 3rd Law
Interaction

35. Which forces are acting to get this guy up in the air?
His feet push DOWN on the ground.
But wait… His downward push can’t be causing his upward motion.

36. Which forces are acting to get this guy up in the air?
His feet push DOWN on the ground.
The ground pushes UP on the man.
There must be a force pushing UP!
The force of the ground pushes him UP!

37. Newton’s 3rd Law of Motion
Newton’s 3rd law says that: For every action force, there is an equal and opposite reaction force.
ALL forces act in PAIRS!
Action Force: Man’s feet push DOWN on the ground.
Reaction Force: Ground pushes UP on the man.

38. Newton’s 3rd Law of Motion
Explain this animation using Newton’s third law.

39. Newton’s 3rd Law of Motion
The man’s foot exerts a backward push on the boat (action force), while the boat exerts a forward push on the man (reaction force).
A PAIR OF FORCES:
EQUAL FORCES, BUT IN OPPOSITE DIRECTIONS

40. Identify the force pairs in each situation
A person fires a rifle.
Action Force – gun pushes the bullet out at high speed.
Reaction Force – the bullet pushes back on the gun (recoil).

41. Identify the force pairs in each situation
A space shuttle lifts off.
Action Force – engine pushes gases down & out.
Reaction Force – the gases push the rocket up.
*This upward force must be stronger than gravity pulling down on the rocket!

42. Identify the force pairs in each situation
A person stands still.
Action Force – gravity pulls the person down to the floor.
Reaction Force – the floor pushes up on the person.
*You don’t need MOTION for force pairs. They are everywhere!

43. If forces are equal and in opposite directions, why don’t they cancel out (and balance)?
Forces only cancel if they act on the same object. (Think about a tug of war – all forces act on the rope).
These forces are acting on different objects!
These forces are acting on different objects!
Action Force – Rocket engine pushing on gases.
Reaction Force – Gases push on the rocket.

44. Think about it . . . Why does it hurt so much when you stub your toe?
When your toe exerts a force on a table, the table exerts an equal force back on your toe.
The harder you hit your toe against it, the more force the the table exerts back on your toe (and the more your toe hurts).

45. What is Momentum? Momentum is a measure of how much motion object has.
It is affected by mass and velocity. The heavier an object is, the more momentum it has.
It’s easier to stop soccer ball coming towards you at 20 m/s than a car coming at 20 m/s.
It’s easier to stop car travelling at 1 km/h than a car travelling 60 km/h!

46. Conservation of Momentum
When objects collide, their total momentum is conserved (stays the same), unless outside forces act.
The total amount of motion coming into a collision will also come out of the collision.

47. Momentum = mass x velocity
Momentum can be calculated using this formula:
Momentum = mass x velocity
A golf ball with a mass of 0.05 kg travels at 16 m/s.
A baseball with a mass of 0.15 kg travels at 7 m/s.
Which ball has the greater momentum?
Golf ball’s momentum = 0.05 kg x 16 m/s
Baseball’s momentum = 0.15 kg x 7 m/s
= 0.8 kg m/s
= 1.05 kg m/s