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# Physics for Kids

## Motion Glossary and Terms

Acceleration - Acceleration is the measurement of the change in an object's velocity. It is equal to the change in velocity over the change in time. Acceleration is a vector.

Collision - A collision in physics occurs when any two objects bump into each other.

Displacement - In physics, displacement refers to an object's overall change in position. It is a vector quantity.

Energy - Energy is the ability to do work. The standard unit of measure for energy is the joule.

First law of motion - The first law of motion states that any object in motion will continue to move in the same direction and speed unless external forces act on it.

Force - Force is the measurement of a push or pull on an object. Force is a vector measured in newtons.

Friction - Friction is the resistance of motion when one object rubs against another. It is a force and is measured in newtons.

Gravity - Gravity is a force caused when the mass of physical bodies attract each other. On Earth gravity pulls at objects with an acceleration of 9.8 m/s2.

Impulse - An impulse is a change in momentum.

Joule - The joule is the standard unit of measure for energy and work.

Kinetic energy - Kinetic energy is the energy an object has due to its motion. It is a scalar quantity calculated using the formula KE = ½ * m * v2, where m = mass and v = velocity.

Mass - Mass is a measurement of how much matter is in an object. It is usually measured in kilograms.

Momentum - Momentum is a measurement of mass in motion. Momentum is equal to the mass times the velocity of an object. It is a vector measured in newton-seconds.

Newton - The newton is the standard unit of measure for force.

Pascal - The pascal is the standard unit of measure for pressure.

Potential energy - Potential energy is the energy stored by an object due to its state or position. It is measured in joules.

Power - Power is a measurement of the rate at which energy is used. Power is calculated by dividing work over time. The standard unit for power is the watt.

Pressure - Pressure is the force over a given area. Pressure is measured in pascals.

Scalar - A scalar is a measurement that only measures the magnitude. Unlike a vector, a scalar does not have direction.

Second law of motion - The second law of motion states that the greater the mass of an object, the more force it will take to accelerate the object.

Simple machine - A simple machine is a basic mechanical device for applying a force and doing work. Some examples of simple machines include the lever, pulley, inclined plane, wedge, and screw.

Speed - Speed is the measurement of how fast on object moves relative to a reference point. It is a scalar quantity measured by distance over time.

Third law of motion - The third law of motion states that for every action there is an equal and opposite reaction.

Vector - A vector is a quantity that has both a magnitude and a direction.

Velocity - Velocity is the rate of change in an object's position. Velocity is a vector quantity. The magnitude of velocity is the object's speed.

Watt - The watt is the standard unit of measure for power.

Weight - Weight is the force of gravity on an object. In physics, weight is measured in newtons.

Work - Work occurs in physics when a force acts on an object to move it some distance. Work is equal to the force times the distance and is measured in joules.

More Physics Subjects on Motion, Work, and Energy

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