Acceleration

rate of change in velocity; can be calculated by dividing the change in the velocity by the time it takes the change to occur.

Air Resistance

force that opposes the motion of objects that move through the air.

Average Speed

total distance an object travels divided by the total time it takes to travel that distance.

Balanced Forces

forces on an object that combine to give a zero net force and do not change the motion of the object.

Displacement

distance and direction of an object's change in position from the starting point.

Force

a push or pull exerted on an object.

Friction

a force that opposes the sliding motion between objects that are in contact.

Instantaneous Speed

speed of an object at a given point in time; is contant for an object moving with constant speed, and changes with time for an object that is slowing down or speeding up.

Net Force

sum of the forces that are acting on an object.

Sliding Friction

frictional force that opposes the motion of two surfaces sliding past each other.

Speed

distance an object travels per unit of time.

Static Friction

 frictional force that prevents two surfaces from sliding past each other.

Unbalanced Forces

forces that combine to produce a net force that is not equal to zero and cause the velocity of an object to change.

Vector

a physical quantity that is specified by both a size and a direction.

Velocity

the speed and direction of a moving object.

Centripetal Acceleration

acceleration of an object toward the center of a curved or circular path.

Centripetal Force

a net force that is directed toward the center of a curved or circular path.

First Law of Motion

states that if the net force on an object is zero, then an object at rest remains at rest, or, if the object is moving, it continues moving with constant velocity.

Gravity

attractive force between two objects that depends on the masses of the objects and the distance between them.

Inertia

resistance of an object to change motion.

Law of Conservation of Momentum

states that if a group of objects exerts forces only on each other, then the total momentum of the objects doesn't change.

Momentum

property of a moving object that equals its mass times its velocity.

Second Law of Motion

states that the acceleration of an object is in the same direction as the net force on the object, and that the acceleration equals the net force divided by the mass.

Third Law of Motion

states that when one object exerts a force on a second object, the second objects exerts force on the first object that is equal in strenght an in the opposite direction.

Weight

gravitational force exerted on an object.