U3W1 FORCES AT WORK

FORCES AT WORK

CHAPTER 1 FORCES A force pushes or pulls something. A force happens when two objects interact, or when one object does something to the other. Forces affect how objects move on Earth and in space. Forces are at work around you all the time. A push is a force that makes the swing move.

You use forces to make things move every day. When you push on a door, it swings open. At the grocery store, a cart moves if you push it. A door closes behind you when you pull it shut. When you pull on a drawer handle, the drawer opens. Pulling is a force that makes the wagon move.

Gravity is a force that pulls objects. You can't see gravity, but you know it is at work. On Earth, gravity pulls objects toward the ground. Gravity pulls you down too. It keeps you from flying into space! You can show the effects of gravity easily. Drop a pencil. What happened? The pencil fell to the ground. Why? Gravity pulled it down. You just proved that gravity works! Because of gravity, the tomatoes push down on the scale.

Friction is another force that affects how things move. It is different from gravity. Gravity works without objects touching each other. But friction is a contact force. It works when two objects rub against each other. lt slows down moving objects. Feel Friction at Work You can feel friction. Rub your hands together quickly. Feel the heat? It is caused by friction. Friction between the mug and the table slows the mug down when you push it.