1. Newton’s First and Second Laws of Motion
Chapter 12 Section 2

2. Newton’s First Law
Also known as The Law of Inertia
The state of motion of an object does not change as long as the net force acting on the object is zero.

3. Newton’s 1st law An object in motion tends to stay in motion
In a straight line at a constant speed
And an object at rest tends to stay at rest
Unless acted upon by an outside force
It requires a push or pull in order to change an objects state of motion!!!

4. Newton’s 1st law
Inertia is the tendency of an object to resist a change in motion.
ESA Video

5. Newton’s 2nd Law
The acceleration of an object is equal to the force you apply divided by the mass of the object.

7. Newton's Second Law
If you apply more force to an object, it accelerates at a higher rate.
Force is directly proportional to acceleration.

8. Newton's Second Law
If an object has more mass it accelerates at a lower rate because mass has inertia.
The more mass the less acceleration; mass is indirectly proportional to acceleration.

9. Newton’s 2nd Law
ESA video #2

10. Newton's Second Law

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

12. Practice Problems
1. What acceleration will result when a 12 N net force applied to a 3 kg object? A 6 kg object?
2. A net force of 16 N causes a mass to accelerate at a rate of 5 m/s2. Determine the mass.
3. How much force is needed to accelerate a 66 kg skier 1 m/sec/sec?
4. What is the force on a 1000 kg elevator that is falling freely at 9.8 m/sec/sec?

13. Practice Problems-ANSWERS
1. What acceleration will result when a 12 N net force applied to a 3 kg object? A 6 kg object?
4m/s 2; 2m/s 2
 2. A net force of 16 N causes a mass to accelerate at a rate of 5 m/s2. Determine the mass.
3.2 kg
3. How much force is needed to accelerate a 66 kg skier 1 m/sec/sec?
66N
4. What is the force on a 1000 kg elevator that is falling freely at 9.8 m/sec/sec?
9800N

14. Now Try on your own!!!

15. Review:
If mass stays the same, and you INCREASE the force applied to an object, what happens to the acceleration of the object?
If the force applied to an object stays the same, but the mass is increased, what happens to the acceleration?

16. Mass Vs. Weight
Mass is the amount of matter present in an object. Measured in Kg.
Weight is the effect of gravity on an object’s mass. Measured in Newtons
Gravity on Earth is 9.8 m/s2 or 9.8 N/Kg)
Mass does NOT change.
Weight DOES change as gravity changes

17. Weight equals mass times the acceleration due to gravity.
W = m x g
Remember, gravity is different on other planets!