1. Newton’s 2nd Law

2. What is acceleration?
What are some examples of acceleration you observe in your every day experiences?
Today: Newton’s 2nd Law

3. Today’s Goal
To begin to explain how force, mass, and acceleration relate to each other.

4. 2nd Law
F = M x A
F = Force, M = Mass, A = acceleration

5. 2nd Law
The net force of an object is equal to the product of its mass and acceleration, or F=ma.

6. F= M x A What does it mean? What is a force? What is mass?
A force is a push or a pull. Anything that makes an object move, or stop moving.
What is mass?
Anything that occupies space

7. What does that mean?
F= M x A
What is an Acceleration?

8. Acceleration Acceleration = speeding up????
Acceleration – the rate at which velocity changes
Can be an:
Increase in speed
Decrease in speed
Change in direction

9. Types of acceleration Increasing speed Decreasing speed
Example: Car speeds up at green light
Decreasing speed
Example: Car slows down at stop light
Changing direction
Example: Car takes turn (can be at constant speed)
screeeeech

10. Question
How can a car be accelerating if its speed is a constant 65 km/h?
If it is changing directions it is accelerating

11. Question
There are 3 controls in a car that make it accelerate. What are they?
Accelerator
Brakes
Steering wheel

12. F= M x A Back to Newton…. Units of Force
When mass is in kilograms and acceleration is in m/s/s, the unit of force is in Newtons (N).
One Newton is equal to the force required to accelerate one kilogram of mass at one meter/second/second.

13. 2nd Law
F= M x A
How much force is needed to accelerate a 1400 kilogram car 2 meters per second/per second?
1) Write the formula
F = m x a
2) Fill in given numbers and units
F = 1400 kg x 2 meters per second/second
3) Solve for the unknown
2800 kg-meters/second/second or 2800 N

14. Newton’s 2nd Law
Force, Mass, and Acceleration are all proportional (F, M, A).
Proportional – always behaves in a predicted way
If one factor changes, you know how the others will change.
i.e. When you change the force, you can predict how acceleration will change.

15. Q: If you change mass, how will it affect A or F
Q: If you change mass, how will it affect A or F? Consider the volleyball and bowling ball (different mass): how will that affect the force you need to achieve the same acceleration? A: you will need more force to push the bowling ball
? = M x A
? = M x A

16. Q: What will happen to the acceleration if you use the same force on the bowling ball and the volley ball?
A: the bowling ball will accelerate slower, and the volley ball will accelerate faster.
F = M x ?
F = M x ?

17. Newton’s 2nd Law is simply an algebraic expression showing how force (F), mass (M), and Acceleration (A) relate to each other:
F= M x A