Forces and Motion Vocabulary

Mass – amount of matter in an object

Weight- the amount that gravity is pulling down on any mass

force- a push or a pull

balanced forces- when the effects of the forces acting on an object cancel each other, no change in motion, net force is zero

unbalanced forces- when the effects of the forces do not cancel each other, there will be a net force, causes motion

net force- the combination of all the forces acting on an object; added if in same direction, subtracted if in opposite directions

Reference point: is the starting point you choose to describe the location, or position of an object.

Position: is an objects distance in a certain direction from a reference point. Must include the objects distance, direction, and reference point.

Distance- (D), the total length traveled, measured in meters (m)

Displacement – the total distance and the direction between the starting and ending points in which you travel.

Speed – (S), equals the distance (d) traveled divided by the time (t) it takes to travel that distance Formula: s=d/t, Measured in units of meters per second (m/s).

Average speed – equals the total distance traveled divided by the total time taken to travel the distance.

Instantaneous speed – the speed of an object at one instant of time

Inertia – tendency of an object to resist change in its motion.

Velocity – (V), speed and direction of a moving object, measured in m/s, with a direction (East, or left etc.)

Acceleration – equals the change in velocity divided by the time or the change to take place; occurs when an object speeds up, slows down, or turns. Formula a= sf-si/t; Units are m/s2.

Positive acceleration- occurs when an object is speeding up, represented by an upward slope on a speed v. time graph

Negative acceleration- deceleration, occurs when an object is slowing down, represented by a downward slope on a speed vs. time graph

Friction- the force that brings nearly everything to a stop; can be rolling, static, or sliding.

Newton 1st law of Motion- If the net force acting on an object is zero, objects at rest will stay at rest and objects in motion will stay in motion, in a straight line at a constant speed. Also known as the law of inertia.

Newton’s second law of motion- The second law states that the greater the mass of an object, the more force it will take to accelerate the object. There is even an equation that says Force = mass x acceleration or F=ma.

Third Law of Motion-for every action, there is an equal and opposite reaction.

gravity- a force that exists between any two objects that have mass gravity- a force that exists between any two objects that have mass. Always pulls objects toward each other

free fall- a falling object is in free fall when the only force acting on the object is gravity

weightlessness- the condition that occurs in free fall when the weight of an object seems to be zero

air resistance- form of friction that acts to slow down any object moving in the air

terminal velocity- when air resistance balances the force of gravity, the object falls at a constant speed

center of mass- the point in an object that moves as if all the object’s mass were concentrated at that point

centripetal force- the force that keeps an object moving in a circle, always points toward the center of the circle.