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SI unit of distance, equal to approximately 39.37 inches


abbreviation for meter

speed equation


speed units

distance unit divided by a time unit, such as meters per second or m/s

instantaneous speed

speed of an object at any instant of time


gives the instantaneous speed when you are riding in a car

average speed

Total distance divided by total time; s=d/t

constant speed

This happens when an object's speed doesn't change for a period of time

distance equation



the speed of an object in a particular direction


a state of change


the rate at which velocity changes over time

acceleration equation

(final speed - initial speed) / time


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

Newton's Law

1. an object at rest willl stay at rest, and an object in motion will stay in motion at constant velocity unless acted upon by an unbalanced force 2. force = massXacceleration 3. for every action there is an equal and opposite reaction


acted upon an object to change an object's speed, direction, or both

balanced forces

2 or more forces exerted on an object that cancel each other out and don't cause a change in motion

unbalanced forces

2 or more forces that effects don't cancel each other out and cause a change in motion

net force

the combination of all forces acting on an object

Newton's First Law

a moving object moves in a straight line with constant speed unless an unbalanced force acts on it


the force that opposes the motion of one surface as it moves across another surface

how to keep object moving when friction is acting upon it

you have to keep pushing or pulling on the object to overcome the frictional force

In what direction is the force of friction exerted?

opposite direction

size of friction force depends on what?

1. 2 surfaces involved
2. The rougher surfaces are, the greater the friction.


the tendency of an object to resist a change in motion

heavy object are harder

to move and stop


a measure of how much matter an object is made of.

Newton's Second Law

if an object is acted upon by a net force, the acceleration of the object will be in the in the direction of the net force, and the acceleration equals the net force divided by the mass.

acceleration equation - Newton's 2nd Law

acceleration (in m/s2) = net force (in N) / mass (in kg)

Newton's Third Law

for every action, there is an equal and opposite reaction, or when one object exerts a force on a 2nd object, the 2nd object exerts equal force in the opposite direction on the first object.

action forces

the force you exert when you push on something

reaction forces

are equal and opposite forces exerted in response to applied forces

force equation - Newton's 2nd Law

force=mass x acceleration

why don't action and reaction forces cancel?

action-reaction forces are equal and opposite, but they act on two different objects

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