Newton’s Laws of Motion

Newton’s First Law The Law of Inertia When the net force is zero, objects at rest stay at rest and objects in motion keep moving with the same speed and direction (velocity).

Inertia The property of matter to resist a change in motion. The more mass an objects has the more inertia the object has. Example-

Changes in motion come from unbalanced forces Unbalanced forces-net force is greater than zero Balanced forces-net force is zero Constant velocity-net force is zero

Newton’s Second Law The acceleration caused by a force is proportional to force and inversely proportional to mass. The more force applied to an object the faster the object accelerates. The more mass an object has the slower the acceleration.

Acceleration Formula a = F/m a = m/s2 F = N(newtons) m = mass(kg)

a = F/m A car has a mass of 1,000kg. If a net force of 2,000N is exerted on the car, what is the car’s acceleration? a = 2,000N/1,000kg, a = 2m/s2 Increase in mass: a = 2,000N/ 1,500kg, a = 1.33m/s2 Decrease in mass: a = 2,000N/500kg, a = 4m/s2

Change in Force a = 2,000N/1,000kg, a = 2m/s2 Increase in force: Decrease in force: a = 1,000N/1,000kg, a = 1m/s2

Acceleration and Force Acceleration is always in the direction of the net force. A positive force causes positive acceleration. Negative force causes negative acceleration (deceleration).

Forces come in matched pairs Newton’s Third Law Forces come in matched pairs Every action force creates a reaction force that is equal and opposite in direction.

Action and reaction forces act on different objects. Example: Throwing a ball The forces do not cancel each other because they act on different objects, the ball and the hand.

Collisions Two objects hit each other, they exert equal and opposite forces Effect of force is not the same More mass, more inertia, less change in motion Objects observe different changes in motion due to inertia, not because the forces are different.

Less massive player experiences a greater change in motion. More massive vehicle experiences a smaller change in velocity.