Newton’s 3 Laws of Motion Sir Isaac Newton developed his famous 3 laws of motion from 1665-1666. 1st Law of Motion: An object at rest will remain at rest, an object in motion will remain in motion at a constant velocity unless acted upon by an outside force. What does this mean?? Inertia -- the property of matter that tends to resist any change in motion (it wants to keep doing what it is doing). An object with a lot of inertia takes a lot of force to start or stop.

If objects in motion tend to stay in motion, why don’t moving objects keep moving forever? Things don’t keep moving forever because there’s almost always an unbalanced force acting upon it. A book sliding across a table slows down and stops because of the force of friction. If you throw a ball upwards it will eventually slow down and fall because of the force of gravity.

2nd Law of Motion Newton’s 2nd Law of Motion states the acceleration of an object is directly proportional to the force acting on the object, and inversely proportional to the mass of the object.

One Newton (1N) = 1 kg x 1 m/sec/sec SAMPLE PROBLEM: What acceleration will result when a 12-N net force is applied to a 1-kg golf ball? A 6-kg bowling ball? Golf Ball: Bowling Ball: One Newton (1N) = 1 kg x 1 m/sec/sec *Notice how the change in mass affects the acceleration when the force applied is the same.

SAMPLE PROBLEM: A Ford minivan has a mass of 1000 kg. A Chevy corvette has a mass of 500 kg. Both cars will accelerate at a rate of 2 m/sec/sec. Find how much force is needed from the engine to move the cars? Mini-Van: Corvette: -when mass is in kg, and acceleration is in m/sec/sec the force is in newtons (N).

2nd Law Review video - (mass and acceleration, force constant)