Did it ever occur to you that tennis, bowling and shopping carts bumping into each other all involve collisions? It is fascinating how just a few rules of physics can predict the outcome of these collisions. You can discover these rules yourself with a fun homemade toy. After creating and playing with the toys in this activity, you will be one step closer to understanding what happens when you hit a tennis ball or go bowling!
Have you ever heard someone say that something “has a lot of momentum?” In everyday language we use “a lot of momentum” to describe things that are hard to stop. In physics an object’s momentum depends on its speed—how fast it moves—and its mass—how much stuff it is made off. Momentum also has a direction—the same direction the object is moving. For an object to gain momentum it can gain speed, gain mass or gain both. To give a shopping cart rolling downhill more momentum, you can make it move faster (increase its speed), load more weight (increase its mass) or do both. You probably intuitively know that the shopping cart with the biggest momentum—the fast-moving, heavily loaded cart—is hardest to stop. It also creates the biggest impact when colliding with something.