Acar moving with a velocity of 20 meters/second has
1.8 * 105 joules of kinetic energy. what is the mass of the car?

Kinetic energy is the energy of an object in motion. It is expressed as the product of its mass and the square of its velocity. The opposite of this energy is called the potential energy, the energy of an object at rest. Calculations are as follows:

KE = mv^2
1.8x10^5 J = m(20 m/s)^2
m = 450 kg