What is used to make a cast of a tool mark ?

Sound is a disturbance that travels through a medium as a

Convection occurs when thermal energy is transferred by the movement of

Abumper car with a mass of 250 kg is traveling at a speed of 4 m/s. this bumper car collides and sticks to a second bumper car with a mass of 250 kg, which is initially at rest. what is the final speed of these two bumper cars after the collision, assuming they remain stuck together?