## Ch. 11 VocabKeylor Piers

Force

A push or pull that acts on an object.

With force, the magnet attracted to the paper clip.

Contact force

A force that requires two pieces of matter to touch.

When we use force, we contact force because we don't have special abilities.

Friction

The force that results when two materials rub against each other or when their contact prevents sliding.

When people rub a piece of coal or a rock against a stick, it makes friction.

Non-contact force

A force that acts at a distance.

Unlike humans, magnets have a non-contact force when they attract to each other.

Gravity

The force of attraction between any to objects.

When I throw this football, it will hit the ground because of gravity.

Acceleration

The rate of which the speed or direction of motion of an object changes over time.

When we are on the highway, we go up to the maximum acceleration that the law will allow.

Inertia

The tendency of an object to resist any change in motion.

If it wasn't for a harness, the inertia would flip me off the roller coaster.

Simple machine

A machine made up of one or two parts.

The belayer in a ropes course uses a simple machine.

Lever

A simple machine in which a bar moves around a fixed point called a fulcrum.

When I was little, I played on a lever called a see-saw.

Pulley

Simple machine consisting of a rope or cable that runs around a grooved wheel.

It would be cool if I had a tree house that has a pulley that drops down a ladde to climb up.

Wheel and axle

Simple machine made up of a circular object attached to a bar.

When you pedal on a bike, the wheel and axel moves.

Inclined plane

Simple machine consisting of a flat surface with one end higher than the other.

If you go outside, you might see an inclined plane, like a ramp.

Wedge

Simple machine made of one or two inclined planes.

An example of a wedge is an axe because of the shape of the point.

Screw

Simple machine consisting of a smooth cylinder with a tiny inclined plane wrapped around it.

I used a screw to make the frame of the window.

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