Force and Motion

Introduction

Force is a push or pull. Force can push or pull an object. It may make the object move. This movement is called motion. Force and motion often work together.

Force and motion happen all the time. They take place everywhere. Force and motion make planets move in space.

An apple falls because of the force of gravity.

Quick Facts

1. Force pushes and pulls objects.

2. Motion involves the movement of objects.

3. Force and motion often work together.

KINDS OF FORCE AND MOTION

Force and motion happen all the time. They take place everywhere. Force and motion make planets move in space. They make the blood move in the body. They make ocean waves move on the beach. They make cars move on the road.

Some kinds of force and motion are hard to see. One of these is gravity. It is one of the most potent forces anywhere. But people cannot see it. Gravity pulls everything downward. A person may drop the ball. Gravity will pull the ball to the ground.

FORCES THAT STOP MOTION

Many forces cause motion. But other forces stop motion.

One force that stops motion is called friction. Friction happens when things rub together. The rubbing makes it hard for things to move.

Even air and water can make it hard to move. A ball thrown in a park must fly through the air. It must push past the air. That makes it harder to move.

Moving through the water is even more challenging. People have to use a lot of force to travel through water.

THE BASICS OF MOTION

Position means where an object is. When the object moves, it changes position. Distance is how far the object moved. It may move a tiny bit or very far. Speed is how fast it moves.

Strong forces may move objects very fast. Weak forces may move them slowly. They may not even move the objects at all.

When a force pushes or pulls an object, the object is likely to move. A pendulum is an excellent example of this.

IMPORTANT PARTS OF THE WORLD

Force and motion take place all the time, all around the world. Earth and other planets move around the sun. The heart forces blood to move around the body. Ocean waves move onto a beach, forcing sand out of the way. Force and motion are essential parts of nature.

Many things in the world are forces in motion. Machines such as automobiles depend on this idea. Cars and trucks zooming on the highway are clearly in motion. The force that is making them move is their engines.

Other kinds of force and motion are not as quickly noticed. One of the most potent forces in nature is gravity, which pulls everything downward. If a person drops the ball, it will move toward the ground because it is pulled down by gravity. People cannot see gravity, but it is everywhere.

FORCES THAT STOP MOTION

Many forces cause motion. When a force pushes or pulls an object, the object is likely to move. Sometimes, though, the object does not move. Some forces prevent or stop motion from happening.

One such force is friction, which occurs when two objects rub together. The rubbing of the objects makes it harder for them to move. If a person pushes a box across the carpet, the person is the force making the box move. But the box is rubbing against the carpet. That rubbing makes friction, which makes it harder to move the box.

Even air and water can create resistance. Resistance means to slow or stop. A dropped object will fall due to the force of gravity. However, the object is falling through the air that pushes up against it. The gravity must pull harder than the air to make the object reach the ground.

Swimmers know that water can also slow motion. Water pushes against people and makes it hard to move. Swimmers have to use more force to be able to move through water than they do to move through the air.

POSITION AND DISTANCE

Position and distance are essential parts of the motion—the place where an object is located in its position. When the object moves, it changes position. The amount of change, or how far the object moves, is called distance. How fast the object moves is called its speed. Strong forces usually move objects at a faster speed than weak forces. This is why a truck can move heavy boxes faster than a person.