I throw a 1 kg rock at 5 m/s.

How much energy does it have?

KE = 12.5 J

Explanation:

Where:

KE=1/2mv^2

KE = kinetic energy

m = mass of a body

v = velocity of a body

Kinetic Energy

Kinetic Energy is the energy an object has owing to its motion. In classical mechanics, kinetic energy (KE) is equal to half of an object's mass (1/2*m) multiplied by the velocity squared. For example, if a an object with a mass of 10 kg (m = 10 kg) is moving at a velocity of 5 meters per second (v = 5 m/s), the kinetic energy is equal to 125 Joules, or (1/2 * 10 kg) * 5 m/s2.

We use Joules, kilograms, and meters per second as our defaults, although any appropriate units for mass (grams, ounces, etc.) or velocity (miles per hour, millimeters per second, etc.) could certainly be used as well - the calculation is the same regardless.