1. Which one would be easier to accelerate by pushing?
Why?

2. Newton’s 2nd Law of Motion
The acceleration of an object depends on the mass of the object and the amount of force applied.

3. Acceleration Depends on Mass
acceleration: decreases as an object’s mass increases … increases as its mass decreases.

4. Acceleration Depends on Force
acceleration of an object: increases as the force applied increases … decreases as the force applied decreases.
The acceleration is
always in the same
direction as the
force applied.

5. The 2nd Law & Math relationship
acceleration (a) … mass (m) … force (F)
F = m x a or
a = F m

6. 2nd Law Problem Solving
1) Determine which equation you will use: F = m x a or a = F / m
2) Replace variables with values given, and solve.
What is the acceleration of a 3 kg mass if a force of N is used to move the mass?
1. For this problem we use a = F/m, because we are looking for the acceleration.
2. a = F/m a = 14.4 N/3 kg a = 4.8 m/s2

7. Your Turn #1
What is the acceleration of a 7 kg mass if a force of 68.6 N is used to move it toward Earth?
For this problem we use a = F/m, because we are looking for the acceleration.
a = F/m
a = 68.6 N / 7 kg
a = 9.8 m/s2

8. Your Turn #2
What force is necessary to accelerate a 1,250 kg car at a rate of 40 m/s2?
For this problem we use F = m x a, because we are looking for the force.
F = m x a
F = 1,250 kg x 40 m/s2
F = 50,000 N

9. Your Turn #3
Calculate the force acting on your 6 kg backpack when the acceleration rate for gravity is 9.8 m/s2?
For this problem we use F = m x a, because we are looking for the force.
F = m x a
F = 6 kg x 9.8 m/s2
F = 58.8 N

10. Comparing two objects (sans friction)
Mass of the car is 1,450 kg a = F/m a = 50 N/1,450 kg a = 0.03 m/s2
Mass of the bike is kg
a = F/m
a = 50 N/14 kg
a = 3.5 m/s2

11. Newton’s Second Law of Motion
Video Demonstration w