A rolling bowling ball and a rolling marble might move at the same speed, but only one of them will knock over your foot. The difference is momentum. Momentum is the amount of motion an object carries. Scientists find it by multiplying an object’s mass by its velocity: p m v p=mv In this formula, p p stands for momentum, m m stands for mass, and v v stands for velocity. Mass is one of the two parts of the formula. So a heavier object moving at the same speed as a lighter one has more momentum. More momentum means the object is harder to stop — and it hits harder when it bumps into something. At this station, you will test that idea. Two toy cars will roll down the same ramp from the same starting height, so they should reach the bottom at about the same velocity. The only difference between them is mass: one car has pennies taped on it. When each car hits a block at the bottom of the ramp, the block gets pushed a certain distance. The farther the block moves, the more momentum the car gave to it.