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Main » Kinematics & Dynamics » Newton's Laws » Lesson I.6.4

### Newton's Laws of Motion - Lesson I.6.4

 Key Terms: Inertia |Galileo's Thought Experiment |

#### Newton's Second Law of Motion

• Often stated as:

When a net force acts on an object, it accelerates in the direct of the net force. The acceleration varies directly to the net force on it and inversely to its mass.

 = net force (N) = acceleration m = mass (kg)

It is important to reduce the mass of the car to insure maximum acceleration.

What is the acceleration of a 1600 kg racecar if the net force was 4500 N?

= 4500 N
m = 1600 kg

What would the acceleration be if the mass was reduced by 150 kg?

= 4500 N
m = 1450 kg

#### Newton's Third Law of Motion

Often stated as:

When one object exerts a force on a second object, the second exerts a force on the first that is equal in magnitude but opposite in direction. These forces are called action-reaction forces.

Or

For every action force there exists a reaction force that is equal in magnitude but opposite in direction.