Newton’s Laws of Motion Sir Issac Newton, , English Scientist

Position = Distance from a Reference Motion = Change in Position Speed = Distance / Time –How fast you are moving –Example: A car travels 100 miles in 2 hours Speed = 100 / 2 = 50 mph Basic Terms

A force is described by 2 parts –Strength –Direction Balanced Forces –Same Strength –Opposite Directions Unbalanced Forces –Sum of all Forces acting on an object is Not Zero, –resulting in a Net Force Push Pull Force

Newton’s 1 st Law of Motion An object at rest stays at rest. An object moving at a constant speed in a straight line will continue moving at a constant speed in a straight line. As long as no net (unbalanced) force acts on it. Inertia is tendency to resist change in motion 1 st Law is also called Law of Inertia

1 st Law Examples With no wind and no atmosphere on the moon, assuming no moonquakes, this footprint on Moon will not change After being launched from earth and given an initial push, this probe traveled about 48 billion miles to Mars, at a constant speed with no engines running.

Acceleration = (change in speed) / Time –How fast your speed is changing Another Basic Term 0 to 60 mph in 3 sec Acceleration = 60 / 3 = 20 mph per sec Lamborghini

Zero Acceleration An object can have No Acceleration 2 ways (1) Speed is a constant, not changing Example –A car moving at a steady speed of 50 mph (2) Speed is zero, not moving Example –A car parked car

Newton’s 2 nd Law of Motion Net Force = Mass x Acceleration Acceleration = (Net Force) / Mass Force on an object is directly related to its Acceleration Increase Force then Acceleration will increase Decrease Force then Acceleration will decrease

A strong force is applied to this tennis ball, it will change direction and accelerate to the right 2 nd Law Examples The stronger the pitcher’s arm, the faster the ball will accelerate toward the batter

Free Fall Without Air Resistance everything falls at the same rate. With Air Resistance heavier objects fall faster. Coffee Filters

Newton’s 3 rd Law of Motion Forces are not “one-sided” Whenever one object exerts a force on a 2 nd object, the 2 nd exerts an equal and opposite force on the 1 st This is often stated as: “to every action there is an equal and opposite reaction” Remember that the “action” force and “reaction” force are acting on different objects

3 rd Law Examples Rocket engine pushes out gases, the gases exert an equal and opposite force back on the rocket Action Reaction Book on a Table Action weight of book Reaction force of table