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Changes in Motion |
A change in motion is caused by an object that moves, stops moving, changes direction, speeds up, or slows down. Unequal forces cause a change in motion. Equal forces cause no motion. An example of an unequal force is when two people are pulling a rope at both ends equally. A see saw is another example of an unequal force when one side pushes harder or is heavier.
Friction is a force that occurs when one object rubs against another. The car’s rubber tires causes friction on the road. Other materials that create friction include a ball rubbing on the floor and rubber pads on in-line skates. Friction can slow things down. Smooth materials don’t rub well and do not create friction. Slippery substances such as oil, soap, and water are used to reduce friction.
Forces cause objects to move in different ways. There are three ways objects can move which are up, down, and in a circular motion. A wave is an up and down movement. The crest is the highest part of the wave. Some examples of waves are water, sound and light waves. A wave can be measured and described by its length. Length is the distance from one crest to another.
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