Force, Motion, and Simple Machines

Vocabulary

• Force- a push or a pull
• Motion- a change in position
• Speed- the measure of how fast something moves over a certain distance
• Gravity- the force that pulls objects towards each other.
• Weight- a measure of the pull of gravity on an object
• Friction- force of resistance between two objects rubbing against each other
• Work- the measure of force it takes to move an object a certain distance
• Simple Machine- a tool that helps people do work
• Lever- a bar that moves on or around a fixed point
• Inclined Plane- a flat surface set at an angle to another surface

There are many forces in the world such as wind blowing on an object, you pulling a wagon, or water pushing on sand.

How much force it takes to pull something is measured with a tool called a spring scale.

When a strong force is applied it can cause an object to move, but not all forces cause motion. Sometimes they are not strong enough.

An example would be an ant trying to push a toy car vs. a child pushing a toy car. Which one will make the car move?

An object will only move if a force is applied to it, and the more strength the force has, the faster the motion will be. This is called speed.

The object will then only stop if another force is applied to it.

So, why does something like a rolling ball eventually stop without you putting your foot on it?

The reason the ball will eventually stop is because of gravity and friction.

These are invisible forces that are acting on the ball as well.

Gravity pulls the ball down against the ground, and friction begins to build between the ball and the ground.

This will eventually cause the ball to slow down and stop.

There are many simple machines in the world that we use without even realizing it.

Many of the things we use in our daily lives have various simple machines in them.