1. GRAVITY
AND NEWTON’S
LAWS OF MOTION

2. Question???? Which object will land sooner
if dropped at the same time,
a tennis ball or a bowling ball?

3. Acceleration Due To Gravity
Objects fall to the ground at the same rate because
the acceleration due to gravity is the same for all
objects.
Bowling ball and tennis ball
The mass of an object does not affect the rate at
which it falls.
Example of acceleration due to gravity

4. ACCELERATING AT A CONSTANT
RATE
All objects accelerate toward Earth at a
rate of 9.8 m/s/s.
WHAT DOES THIS MEAN?
This means that for every second an object falls, the object’s downward velocity increases by 9.8 m/s.

5. Acceleration Due To Gravity
Objects fall to the ground at the same rate because
the acceleration due to gravity is the same for all
objects.
The mass of an object does not affect the rate at
which it falls.
All objects accelerate toward Earth at a rate of 9.8 m/s/s.

6. What happens when I drop a tennis ball and a piece of paper??
Is there something else acting on the paper to cause it to not fall like the tennis ball? What?

7. DOES AIR RESISTANCE AFFECT FALLING OBJECTS?
Yes!!
THE FORCE OF GRAVITY PULLS OBJECTS
DOWNWARD AS THE FORCE OF AIR
RESISTANCE PUSHES IT UPWARD.
FREE FALL- when an object is being pulled down by gravity,
but no other forces are acting on it.
Does free fall occur with air resistance?

8. Example of acceleration due to gravity

9. Gravity, Free Fall, and Air Resistance
Gravity - the force that pulls objects toward
one another.
Free Fall – when only gravity is acting on an
object. This is rare because of air resistance.
All objects free fall at a rate of 9.8 m/s. A
golf ball and basketball will hit the ground
at the same time.
Air Resistance – type of fluid friction which
increases with the surface area of the object.

10. Record this definition in your notes:
Balanced forces are two forces acting in opposite directions on an object, and equal in size. Anytime there is a balanced force on an object, the object stays still or continues moving at the same speed and in the same direction.

11. So…
When balanced forces act on an object at rest, the object will not move. If you push against a wall, the wall pushes back with an equal but opposite force. Neither you nor the wall will move.

12. So…
What do you think an UNBALANCED force is?

13. Record in your notes:
Forces that cause a change in the motion of an object are unbalanced forces (therefore the forces are not equal) What examples can you think of? -braking on your bicycle to stop moving (or to slow down) -pushing a bowling ball down the hall

14. NEWTON’S LAWS OF MOTION

15. Newton’s Laws of Motion
Brainpop

16. NEWTON’S FIRST LAW OF MOTION
AKA: LAW OF INERTIA
An object at rest remains at rest and an
object in motion remains in motion at constant
speed and in a straight line unless acted on by
an unbalanced force.
Examples:
The man will remain in motion
until a force stops his
movement.
A golf ball on a tee.

17. Also called: LAW OF INERTIA
Title your notebook: “Newton’s Laws of Motion”
Also called: LAW OF INERTIA
Inertia is the tendency of all objects to resist any change in motion.

19. NEWTON’S SECOND LAW OF MOTION
The acceleration of an object depends on the mass
of the object and amount of force applied.
FORCE=MASS X ACCELERATION
Or a=F/m
How does Newton’s
Second Law explain why
the shuttle’s acceleration
increases during takeoff?

20. Bell Ringer- explain what happened?

22. Newton’s 2nd Law of Motion
Newton’s 2nd law of motion: FORCE = MASS X ACCELERATION F = ma How much an object accelerates depends upon the mass of the object & how much force is applied

23. The greater mass or velocity an object has, the greater its inertia.
You can test this the next time you're at the grocery store! It takes a strong push to get a loaded shopping cart moving, but once it gathers speed it keeps going, even if you let go of the handle When you stop a moving cart full of groceries, it takes much more force to stop it than an empty cart.
Why? (it has more mass).

24. Momentum=mass x velocity
WHAT IS MOMENTUM?
MOMENTUM is a property of a moving object that depends on
the object’s mass and velocity.
Momentum=mass x velocity
THE MORE MOMENTUM AN OBJECT HAS, THE
HARDER IT IS TO STOP THE OBJECT OR
CHANGE ITS DIRECTION.

25. Bell Ringer -When the driver slams the brakes, why does the man lurch forward?

26. Cause & Effect
What causes the balloon rocket to work?

27. NEWTON’S THIRD LAW OF MOTION
For every action there is an equal and
opposite reaction.
FORCES ALWAYS ACT IN PAIRS.
The action force is the swimmer’s
hand and feet pushing the water.
The reaction force is the water
pushing on the swimmer’s hands and
feet.

28. According to Newton, whenever objects A and B interact with each other, they exert forces upon each other.
When you sit in your chair, your body exerts a downward force on the chair and the chair exerts an upward force on your body.

29. Flying gracefully through the air, birds depend on Newton’s third law of motion. As the birds push down on the air with their wings, the air pushes their wings up and gives them lift.

30. MORE EXAMPLES OF ACTION AND REACTION FORCE PAIRS
The rabbit’s legs exert a force on
Earth. Earth exerts an equal force
on the rabbit’s legs, causing the
rabbit to accelerate upward.
The shuttle’s thrusters push the exhaust gases downward as the gases push the shuttle upward with an equal force.

31. You put force on chair, chair pushes back up on you
Ms. Dennis and Rufus push on scale
Bird pushes down on air, air resistance pushes back up

33. LET’S
PRACTICE

34. What happened to cause the action/reaction between the basketball and soft ball?
Draw or describe what is the action & what is the reaction?

35. Explain Newton’s First Law of Motion using this picture.
A plane will not soar in the air unless it is pushed by the
exhaust from its jet engines.

36. Newton’s Second Law of Motion
- Which would you have to apply a greater
force to stop and go?
- Which would you rather buy gas for?
Which would you rather be driving in a
head-on collision?

37. Bell Ringer:
NEWTON’S THIRD LAW OF MOTION
LIST and DESCRIBE the action and reaction
forces in the following picture.

39. Bell Ringer What is Newton’s 2nd Law of Motion?
How do you think Nasa scientists use Newton’s 2nd Law when designing space shuttles?

40. Rocket link

41. Rocket
Which of Newton’s Laws will you need to use when designing your rocket? Why?
What will happen if you make your rocket too heavy?
What will happen if you do not seal your rocket completely?
What will happen if you make your rocket took loose (loosely rolled)?

42. Key words for each law:
1st Law = “straight line”, “continues”, “inertia”, “rest”
2nd Law = “faster”, “acceleration”, “mass”, “force”. Ask yourself: is there a force? Is more force needed for objects of different masses? Are there 2 things being compared?
3rd Law = “action/reaction”, ask yourself: are two objects pushing off of each other & then moving in opposite directions?

43. Examples of each law:
An object at rest stays at rest & an object in motion will stay in motion (unless acted on by another force)
1st: You set a book on your table before bed; it has not moved when you see it again the next morning

44. Examples of each law:
An object at rest stays at rest & an object in motion will stay in motion (unless acted on by another force)
1st: You set a book on your table before bed; it has not moved when you see it again the next morning

45. Examples of 2nd law:
The more massive an object is, the more force that is required to accelerate it OR the more force used, the farther an object will go
2nd: Mrs. Massey throws a ball as hard as she can, and it lands on the roof! Then, she throws the same ball as gently as she can, and it lands only one foot in front of her.

46. Examples of 3rd Law:
Alec’s feet push off the gym floor to jump into the air. Alec’s feet push off a skate board to jump into the air, and the skateboard flies backward.

47. Get out your homework