You will be able to: ● Identify and describe the changes in position, direction, and speed of

an object when acted upon by unbalanced forces.

● Identify balanced and unbalanced forces.

Adapted from a PowerPoint by Kathleen Ingram, Lamar Middle School

What are some common What are some common forces?forces?

GravityGravity – the force with which the earth, moon, or another massive object attracts another object towards itself.

What are some common What are some common forces?forces?

Normal forceNormal force – a support force exerted upon an object in contact to another object.

Net ForceNet ForceThe net force is the combined effect of all

forces acting on an object.

ForceForceBalanced ForcesBalanced Forces

forces acting on an object that are opposite in direction and equal in size

no change in speed

ForceForceUnbalanced forcesUnbalanced forces unbalanced forces that are not opposite and

equal velocity changes (object accelerates)

Ffriction

W

Fpull

Fnet

NN

Are there different forces acting on the figure skaters?

What direction are the forces acting?Are the forces balanced or unbalanced? How do

you know?

Today we will demonstrate…(A) basic relationships between force and

motion using simple machines including pulleys and levers

(A) that an object will remain at rest or move at a constant speed and in a straight line if it is not being subjected to an unbalanced force

(B) how unbalanced forces cause changes in the speed or direction of an object's motion

Tug of Wardrawing

Force Problems

What is the net force?

Are the forces balanced or unbalanced?

Describe the motion of the object. (none, accelerate to left, accelerate to right)

20 N20 N

Force Problems

What is the net force?

Are the forces balanced or unbalanced?

Describe the motion of the object. (none, accelerate to left, accelerate to right)

20 N 30 N

Force Problems

What is the net force?

Are the forces balanced or unbalanced?

Describe the motion of the object. (none, accelerate to left, accelerate to right)

20 N 10 N

Force Problems

What is the net force?

Are the forces balanced or unbalanced?

Describe the motion of the object. (none, accelerate to left, accelerate to right)

20 N 30 N

Force Problems

What is the net force?

Are the forces balanced or unbalanced?

Describe the motion of the object. (none, accelerate to left, accelerate to right)

30 N 30 N

Balanced and unbalanced Balanced and unbalanced forcesforceshttp://www.engineeringinteract.org/resources/parkworldplot/flash/concepts/balancedandun.htm