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3rd Law of Motion

UC Irvine Physics and Astronomy Videos

School blocks YouTube? Download file below.

Sailboat.flv or Force - Sailboat.m4v

 

Review

Click on the button below to start the game.

One of these things is not like the other!

 

The idea for this game and the graphic above come from a great physics teacher named Kelly O'Shea.

 

 

B) Free Body Diagrams - diagrams that show the forces acting on an object

 

Ex 1) Lamp on a table

                                                         
 

        [ Flash ]       

Fn - normal force

 

(1) upward force supporting on an object

 

(2) Always drawn perpendicular  to surface where 2 objects meet

 

(3) When an object is placed on a horizontal surface

 

Fn = weight of object

 

 

 

 

Object Resting on an
Incline Plane

weight force?

Normal Force?

Friction?

 

 

 

Weight force? B

Normal Force? C

Friction? D

 

 

 

 

Ex 2) Object at rest on an incline plane

 

Drag and Drop the vector arrows to show the forces acting on a box resting on a ramp.

 

Click on the picture above

 

 

 

On A Ramp,
 
Fn (normal force) ≠ Weight Force

(Fn is less)

 

 

 

Calculating the Components of
Weight Relative to a Ramp

| Onsite |

by Dr. Michael R. Gallis - Penn State Schuylkill

 
Penn State   Schuylkill

Go Nittany Lions!!

 

 

[Flash]
 St. Mary's H.S.

 

Ranking Task

Rank the parallel component on the boxes below, from largest to smallest. Justify your answer.

 

 

 

Ex 3) Force on a falling object
(before terminal velocity)

 

 

 

 

Downward Force - Weight Force

 

Upward Force - Friction

 

 

 

 

 

 

Ex 4) Block being pulled to the right at constant velocity

What force is on this block that is also on you?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Now draw the applied force

 

 

 

 

 

 

 

Draw the last force

 

 

 

 

 

 

Last force is the friction force

 

 

 

 

 


Fnet = 0
 
(Always True at
 Constant Velocity)

 

 

 

 

 

How could this box be moving if
all the forces are balanced?

 

 

 

 

 

 

 

 

A force is not required
to MAINTAIN motion

 

 

 

 

 

 

Ex 5) Forces on a projectile moving from left to right

 

 

What force is on this ball that is also on you?









 


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 








 

 

 

 

 

 

If there is no forward force on this ball,
how could it move forward?

- Aristotle

Aristotle - (384 BC – 322 BC) was a Greek philosopher

Della Porta Collection then Borghese Collection; purchased in 1807

 

 

 

 

English: Portrait of Galileo Galilei by Justus Sustermans painted in 1636.

 

Galileo (and Newton) would say ...

 

 

 

An object in motion
doesn't require
a force to stay in motion

 

 

 

 

 

I Will Derive!!

 

 

 

Review

Which plots below represent an object in a state of equilibrium?

 

 

 

 

 

 

A, C, D

 

 

 

Gravity

 

 

 

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