Energy Forces and Newton's Laws

What is energy?

The capacity to perform work.

What is work?

A force applied over a distance in the direction of the force.

What unit measures energy and work?

The joule (J).

What is power?

The rate at which energy is used — work divided by time.

What unit measures power?

The watt.

What is the conservation law of energy?

Energy is neither created nor destroyed, only transformed into other forms.

What is the total energy in a system equal to?

The sum of its kinetic energy and its potential energy.

What is kinetic energy?

Energy associated with movement and motion.

What is potential energy?

Energy associated with the relative position of objects in a system.

What is the formula for kinetic energy?

KE = one half times mass times velocity squared.

What is the formula for gravitational potential energy?

U = mgh, where m is mass, g is acceleration due to gravity, and h is height above the ground.

What is a force?

Something that causes a change in the motion of an object.

What are the four fundamental forces?

Gravity, the electromagnetic force, the nuclear weak force and the nuclear strong force.

What unit measures force?

The newton (N) — one newton equals one kilogram meter per second squared.

How does the force of gravity relate to mass and distance?

Directly proportional to the product of the two masses, and inversely proportional to the square of the distance between them.

How does the electromagnetic force relate to charge and distance?

Equal to the product of the two charges and inversely proportional to the square of the distance between them.

What is Newton's first law?

An object at rest stays at rest and an object in motion stays in motion unless acted on by a force.

What is Newton's first law also called?

The law of inertia.

What is Newton's second law?

Force is directly proportional to acceleration; a mass experiencing a force undergoes acceleration. F = ma.

What is Newton's third law?

For every action there is an equal and opposite reaction.

Which of Newton's laws explains a rocket pushing off its exhaust?

The third — equal and opposite reaction.

Which of Newton's laws explains why you lurch forward when a car brakes?

The first — inertia.