Mass, energy and keeping safe in collisions

Mass tells how much stuff, or matter, an object is made of. A truck has much more mass than a small car, and a cricket ball has more mass than a table-tennis ball. If two objects move at the same speed, the one with more mass has more kinetic energy. A truck with a mass of 2 tonnes has twice the kinetic energy of a 1-tonne truck moving at the same speed. So when a heavy object hits something, it passes on more energy and causes a bigger change. This is why big trucks need bigger engines, and why the driver of a heavy vehicle must take extra care. To test it, we roll a light toy car and then the same car with coins taped on it down the same ramp into a paper cup. We measure how far the cup moves each time.