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

Ex 1) Lamp on a table

                                                         
 
               

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

 

 

 

 

 

 

Ex 2) Object on an incline plane

 

Box on Ramp (larger) - St. Mary's HS

On ramp, Fn (normal force) does not equal weight force  ( not horizontal)

Free Body Diagram - St. Mary's HS

 

Free Body Diagram - Penn State Schuylkill

 

 

 

 

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

 

 

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

 

 

 

 

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

 

 

 

manFalling