FORCES

A force is a push or a pull on an object.

Every force has strength, magnitude and

direction.

Forces acting on a stationary object can set

the object in motion.

They can also change the object’s speed or

the direction it is moving in.

Forces can also change the shape of a

stationary object.

GRAV

ITY Why do things fall to the

ground?Gravity is the force of attraction

between all objects that have

mass.The strength of gravity

between two objects depends

on two things: the mass of the

objects and the distance

between them.

Ele

ctri

c and

Magneti

c Fo

rces

These forces are closely

related.Both are cause by negative and positive

charges in matter.Electric forces are associated with unmoving charges.

Magnetic forces are created by moving electric chages.

Fric

tion

-Friction is the force that opposes

motion between two surfaces that

are in contact with each other.

-Friction might prevent motion

from starting, or it might oppose

motion in progress.-Types of friction include sliding,

rolling, static and fluid.

Bala

nce

d a

nd

Unbala

nce

d F

orc

es

-More than one force can – and

usually does- act on an object at

the same time.-Sometimes these forces are

applied in the same direction.

-Sometimes the forces are applied

in different directions.-The net force on an object is the

combination of all the forces

acting on it.-Force is measured in newtons.

-Force is shown with arrows.

Bala

nce

d F

orc

es

-When the net force is zero, the

forces are said to be balanced.

Balanced forces produce no

change in the motion of an object.

-An object that is not moving will

stay motionless, while an object

that is moving will maintain its

speed and direction. Balanced

forces can, however, crush an

object.

Unbala

nce

d

Forc

es

-When the net force on an object is

greater than zero, the forces are

said to be unbalanced.

Unbalanced forces produce a

change in the motion of an object.

- A motionless object will begin to

move, while an object already

moving will change its speed

and/or direction.

Calc

ula

ting

Net

Forc

e-To find the net force of forces that

are acting in the same direction,

simply add them together.

-to find the net force of forces that

are acting in opposite directions,

simply subtract the smaller force

from the larger one.