1. Newton’s Second Law of Motion
An object’s acceleration depends on its mass and the force applied to it
Force = mass x acceleration
Fnet = m x a
When force is constant…
Greater mass = slower acceleration
Smaller mass = greater acceleration

2. Newtons
1 Newton is defined as the amount of force required to accelerate a 1-kg object at a rate of 1 m/s2.
1 N = kg*m/s2

3. Example
If 2 objects are pushed with the same force, which would have the greater acceleration?
m = 14 g
m = 0.5g

4. Example
What is the force of a truck if it has a mass of 100 kg and an acceleration of 10 m/s2?

5. Group Practice Net Force Mass Acceleration 10 N 2 kg ? 20 N 4 kg
5 m/s2
10 m/s2
Based on the table above, what relationships do you see between force, mass, and acceleration?

6. Group Practice Net Force Mass Acceleration 10 N 2 kg 5 m/s2 20 N
Based on the table above, what relationships do you see between force, mass, and acceleration?

7. Mass vs. Weight
Mass: quantity dependent on the amount of matter present in an object
Units = kg
MASS NEVER CHANGES
Weight: the FORCE of gravity with which Earth attracts an object towards itself
Units = N
WEIGHT DEPENDS ON GRAVITY
When a = g, the force you are solving for is weight

8. Example
Scooby-Doo has a mass of 15 kg. What is his weight on earth?

9. Example 1
12 N
If the object above accelerates at a rate of 12 m/s2, what is the object’s mass?
.33 kg

10. Question #5
If a woman has a mass of 60 kg, what is her weight on earth in Newtons?
588 N

11. Question #6
If an object weighs 250 N on the surface of earth, what is its mass?
25.5 kg

12. Question #7
An object weighing 845 Newtons on earth weighs 140 Newtons on the surface of the moon. Calculate the magnitude of the acceleration due to gravity on the moon.
1.62 m/s2

13. Question #8
A kilogram baseball, initially moving at 15 meters per second, is brought to rest in second by a baseball glove on a catcher’s hand. What is the magnitude of the average force exerted on the ball by the glove?
56 N