Forces Motion Forces n Forces are acting all

• Slides: 7

Forces & Motion Forces

n Forces are acting all around you. n Objects, including you, are being pushed and pulled in different directions. n Sometimes forces cause motion: – sliding a chair, throwing or kicking a ball, pushing a grocery cart n More importantly, stationary objects (objects sitting still) have forces acting on them too – a pop can on the counter, a picture frame on the wall, computer on the desk

n Objects exert forces on each other: – You are exerting a force on your chair, AND you chair is exerting a force equally on you. n Forces have magnitude and strength. n Strength is measured in Newtons (named after Sir Isaac Newton)

n Forces affect objects in several ways… – Forces acting on stationary objects can set the object in motion (wind = forces that blows over a trash can). – Forces can change a moving object’s speed and or direction it’s moving (you get hit in the head with a ball – your head (outside force) changes the direction and speed that the ball was going). – A force can affect an object without making it move (balanced forces) – Forces can change a stationary object’s shape (squeezing a balloon)

Gravity is a force. n Gravity acts on all objects that have mass. n All objects have mass. n The strength of gravity depends on two things: – The mass of the object. – The distance between two objects. n Mass is the measure of the amount of ‘stuff’ inside an object n The greater the mass of either object, the stronger the gravity between them.

Friction is a force n Friction is a force that opposes motion between two surfaces that are in contact with each other. – Friction may prevent motion from starting, it may slow motion down, it may even stop it n When two solid surfaces slide against each other, it is known as sliding friction. n When two solid surfaces roll over one another, it is known as rolling friction.

n When a solid surface passes through air or water, it is known as fluid friction. n Friction depends on two things: – The type of surfaces involved. – How hard the surfaces are pressing on one another.