How many joules of kinetic energy does a 750 kg car traveling at 65 mi hr have. By what factor would its kinetic energy decreases if the car travel half as fast?

For this question, we will use the formula K = 1\2 mv2. But first, we must convert the 65 miles per hour into meters per second. Multiply miles per hour by a factor of 1.609 to get kilometers per hour. Divide this answer by 3600 to get kilometers per second. Multiply this by 1000 to get meters per second. In this case, the velocity in meters per second is aproxamitely 29 meters per second. To get the kinetic energy, we multiply one half, times the mass 750 kg, times 292 meters per second. This yields 315375 Joules. If we halved the velocity, the kinetic energy would be one-fourth that of the original kinetic energy. This is because the velocity is squared. This holds true if we go to one third the original speed. Then it would be one-ninth of the original kinetic energy.