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« B         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.            