1. Section 2.2 Force and mass determine acceleration.

2. Vocabulary
___________________________ states that the acceleration of an object increases with increased force and decreases with increased mass.
Newton’s Second Law

3. So… Increasing Mass Decreases Acceleration!
Which shopping cart will have more acceleration if the same force is applied to both carts?
So… Increasing Mass Decreases Acceleration!
small mass
same size force
large mass
same size force
greater acceleration
smaller acceleration

4. So… Increasing Force Increases Acceleration!
Which shopping cart will have more acceleration?
So… Increasing Force Increases Acceleration!
same mass
same mass
greater force
smaller force
greater acceleration
smaller acceleration

5. The apple will accelerate more because it has less mass.
An apple and a bowling ball are pushed with the same force. Which one will accelerate more? Why?
The apple will accelerate more because it has less mass.

6. Calculating Force
F = ma
F = force
m = mass
a = acceleration

7. Calculating Force Class Example
What force is needed to accelerate a 10 kg shopping cart 3 m/s2?
F = m x a
F = 10 kg x 3 m/s2
F = 30 N

8. Calculating Force Practice Problem #1
If a 5 kg ball is accelerating 1.2 m/s2, what is the force on it?
F = 5 kg x 1.2 m/s2
F = 6 N

9. Calculating Force Practice Problem #2
A person on a scooter is accelerating 2 m/s2. If the person has a mass of 50 kg, how much force is acting on that person?
F = 50 kg x 2 m/s2
F = 100 N

10. Calculating Acceleration
What would the equation look like if I knew the force and the mass, but needed to find the acceleration?

11. Calculating Acceleration Class Example
If a team pulls with a combined force of N on an airplane with a mass of kg, what is the acceleration of the airplane?
a = 0.3 m/s2

12. Calculating Acceleration Practice Problem #1
Half the people on the team decide not to pull the airplane. The combined force of those left is N, while the airplane’s mass is still kg. What will be the acceleration?
a = 0.15 m/s2

13. Calculating Acceleration Practice Problem #2
A girl pulls a wheeled backpack with a force of 3 N. If the back pack has a mass of 6 kg, what is its acceleration?
a = 0.5 m/s2

14. Calculating Mass
What would the equation look like if I knew the force and the acceleration, but needed to find the mass?

15. Calculating Mass Class Example
A model rocket is accelerating at 2 m/s2. The force on it is 1 N. What is the mass of the rocket?
m = 0.5 kg

16. Calculating Mass Practice Problem #1
Another model rocket is accelerating at a rate of 3 m/s2 with a force of N. What is the mass of the rocket?
m = 0.3 kg

17. Calculating Mass Practice Problem #2
A boy pushes a sign with a force of 10 N, and the sign accelerates 2 m/s2. What is the mass of the sign?
m = 5 kg

18. Thinking Question It can simply change direction!
How can an object accelerate when it does not change speed?
It can simply change direction!

19. True or False? _____ A force can make an object change direction.
_____ If an object only changes direction then it is not accelerating.
_____ An object moves in the direction the force is applied.
_____ Forces can cause acceleration.
True
False
True
True

20. Vocabulary
Any force that keeps an object moving in a circle is known as _____________ force.
centripetal

21. Where does the force point towards?
If you let go of the string, the ball would fly off in the direction it was headed when you let go. This is called the path of inertia.

22. What do the blue arrows represent?
centripetal force
What do the black arrows represent?
The path of inertia