1. Newton’s Second Law of Motion
How fast does it go?
Newton’s Second Law of Motion

2. Acceleration
An unbalanced force causes something to accelerate.

3. Acceleration
Acceleration is directly related to the size and direction of the force.
It accelerates in the direction you push or pull it.

4. In other words….
Large Force = Large Acceleration F a

5. So….if you push twice as hard, it accelerates twice as much.
In other words….
Small Force = Small Acceleration F a
So….if you push twice as hard, it accelerates twice as much.

6. But there is a twist….
Acceleration is INVERSELY related to the mass of the object.

7. In other words…..using the same amount of force….
Small acceleration a
Large Mass
Large acceleration F a
Small Mass

8. Newton’s Second Law
Newton, genius that he was, observed these “rules” of acceleration and came up with his second law of motion. It is both a formula & a law.

9. Newton’s Second Law
The acceleration of an object depends on the mass of the object and the amount of force applied.
F = ma
Force = Mass x Acceleration

10. Newton’s Second Law Key Point #1:
Increased force  increased acceleration
Key point #2:
Increased mass  decreased acceleration (for the same amount of force)

11. Golf Ball vs Ping Pong Ball - DEMO

12. Golf Ball vs Ping Pong Ball - DEMO
They fall at the same time because… Gravity accelerates the two objects at equal rates

13. Sample Problem – Calculate the acceleration of an apple and watermelon when dropped off of a building.
Mass = 1.02 Kg
Force = 10 N
Mass = .102 kg
Force = 1 N

14. Sample Problem
So the objects have equal acceleration – they both accelerate at -9.8m/s² (due t0 gravity)

15. Hmm… does this mean they would land at the same time if dropped off of a building?

16. Hmm… does this mean they would land at the same time if dropped off of a building?
Why don’t we actually observe all objects falling at the same rate in Earth’s atmosphere?

17. Hmm… does this mean they would land at the same time if dropped off of a building?
Why don’t we actually observe all objects falling at the same rate in Earth’s atmosphere?
Air resistance slows down acceleration.
Air resistance is a type of fluid friction.
The amount of air resistance depends on the size and shape of the object.
Example: Feather vs Apple

18. Practice Problems

19. Lab Instructions
Measure the TIME it takes for the car to travel the distance of the counter
PART 1:
Pull with 1 oz fishing weight
Put 100 grams in car
Repeat with 500 grams
PART 2:
Put 500 grams in car
Pull with 2 oz fishing weight

20. Let’s see it in action…

21. Lab Data
PART 1:
PART 2:

22. Lab materials

23. Lab set-up

24. Procedures
Assemble the book and ramp (ruler) as shown in your diagram.
Place the larger marble at the bottom of your ramp.
Drop the smaller marble from the top of your ramp.
Time how long it takes the larger marble to reach the end of the ramp. Record data below.
Place the smaller marble at the bottom of the ramp.
Drop the larger marble from the top of your ramp.
Time how long it takes the smaller marble to reach the end of the ramp. Record data below.

25. Data Table

26. Have fun but… don’t lose your marbles! 