Forces and Motion

Ouch! Why does it hurt so much when you stub your toe? Banging into a wall is painful. Your toe hurts because something heavy and solid made it change speed very quickly. The wall put a force on your toe. A very painful force!

Forces are around us every day. Every time something starts to move or stops moving, that change happens because a force has acted on it. But what are these forces? And how are they related to motion?

Forces and Motion

A force is anything that pushes or pulls on an object. You feel forces all the time. When you walk, your feet push on the ground to move you forward. When you hold a pencil, your fingers push against the pencil to keep it in place. Even when you’re lying down, you’re still feeling the force of gravity. Gravity is the force that pulls you down to Earth.

Sometimes, forces act when two things touch. When you stub your toe on a wall, the painful force happens through touch. Other forces can act over a distance. These forces don’t need to touch anything to be felt. Gravity is a force that doesn’t need to touch something to make it move. The force from a magnet is another type of force that can act over a distance.

Forces and motion are related through changes in speed. These changes in speed are called accelerations. Even something slowing down is called an acceleration.

Larry Giles is the Vice President for Engineering at Busch Gardens, an amusement park in Williamsburg, Virginia. “Accelerations can be any direction,” he explained. Accelerations can come up, down, left, right, forward, backward, or any combination of those directions.

Your stubbed toe hurts because it came to a sudden stop against the wall. When something changes speed, the force on the object changes, too. That acceleration is because the wall pushed on your toe. That push — or that force — hurts!

But forces aren’t always painful. Sometimes, forces can be a lot of fun.

Forces in Different Directions

People all over the world love spinning, swooping, and screaming their way through amusement parks. Many people think it’s worth standing in long lines to feel the different ways that rides push and pull on our bodies. Acceleration and forces that happen in unusual directions are what make amusement park rides so fun.

Our bodies are used to moving in certain ways. We don’t think of riding in a car as scary because we’re used to the accelerations — and the forces that go along with them — caused by those motions. But rides in amusement parks are designed to change speeds in directions that we don’t usually experience. “That’s where everyone says, ‘oh my gosh, this is so scary!’” said Larry.

Most roller coasters and amusement park rides go more slowly than a car on the highway. We think the rides are exciting because of the different ways they change speeds and apply forces to our bodies.

Whether they are fast or slow, constant or sudden, forces are all around us. They put our lives in motion!