1. Newton’s Second Law of Motion

2. Different Forces
Suppose you are at lunch with a friend, and they ask you to pass the milk.
Think of how hard you would have to push a small carton of milk to get it to your friend.
Now, suppose you are at dinner with your family, and they ask you to pass the gallon of milk.
Think of how much more force you would need to use to push the gallon of milk.
The same force will cause an object with less mass to accelerate less.

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

4. Newton’s Second Law
Newton studied how objects moved, and he noticed some patterns.
The acceleration of an object depends on the mass of the object and the size of the force applied to it.
Newton’s Second Law:
Force = Mass x Acceleration

5. Units Item being measured Units Force Newton N Mass Kilograms kg
Acceleration
Meters/second squared m/s2

6. Example What force is needed to move a 10 kg object at 4 m/s2?
1st Write the equation you will be using
F = M x A
2nd Fill in the equation with what you know from the problem
F = 10 kg x 4 m/s2
3rd Do the Math
10 x 4 = 40
4th Write your answer with units
F = 40N

7. Example What force is needed to move a 13 kg object at 8 m/s2?
1st Write the equation you will be using
F = M x A
2nd Fill in the equation with what you know from the problem
F = 13 kg x 8 m/s2
3rd Do the Math
13 x 8 = 40
4th Write your answer with units
F = 104N

8. Other Discoveries
Newton’s equation can also be manipulated to find acceleration or mass.
Acceleration = force / mass
Mass = force/acceleration
Same units!

9. Examples
What is the acceleration of a baseball that weighs 1.5 kg and is hit with 15 N of force.
1st Write the equation you will be using
A = F/M
2nd Fill in the equation with what you know from the problem
A = 15N / 1.5kg
3rd Do the Math
15/1.5 = 10
4th Write your answer with units
A = 10 m/s2

10. You Try! 1. F= ? M= 17 kg A= 7 m/s2 2. F= 5N M= 8 kg A= ?
3. F= 10 N M= ? A= 17 m/s2
4. F= ? M= 65 kg A = 100 m/s2

11. What are the proper units for acceleration?
A. N
B. Kg
C. m/s2
D. m/s3

12. What are the proper units for force?
A. N
B. Kg
C. m/s2
D. m/s3

13. What are the proper units for mass?
A. N
B. Kg
C. m/s2
D. m/s3

14. If you apply the same force to a bowling ball and a tennis ball, which one will accelerate faster?
B. Bowling Ball