UNIT 3

UNIT 3

NEWTON’S LAWS

NEWTON’S LAWS

1st

NOTES

2nd

3rd

Objects in motion stay in motion and objects at rest

stay at rest unless acted upon by an unbalanced

force.

F = m* a

For every action

there is an equal

and opposite

reaction.

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UNIT 3

FBD

FREE BODY DIAGRAMS

1. Picture the situation in your head (or draw!)

2. Draw a dot to represent the object

3. Draw the forces as vectors acting on the object

a. Does the object have weight?

b. Is the object sitting on a surface?

c. Is the object being pushed or pulled

somehow? How many ways?

d. Does the problem tell us there is friction?

NOTES

FREE BODY DIAGRAMSEXAMPLE

FREE BODY DIAGRAMS

1. Picture the situation in your head (or draw!)

NOTES

FREE BODY DIAGRAMS

2. Draw a dot to represent the object

NOTES

FREE BODY DIAGRAMS

3. Draw the forces as vectors!

NOTES

a. Does the object have weight? YES!

Fg

FREE BODY DIAGRAMS

3. Draw the forces as vectors!

NOTES

b. Is the object sitting on a surface? NO!

Fg

So no normal force!

FREE BODY DIAGRAMS

3. Draw the forces as vectors!

NOTES

c. Is the object being pushed or pulled?

YES!

Fg

How many ways?

1 way!

Which way?UP!

Fa

FREE BODY DIAGRAMS

3. Draw the forces as vectors!

NOTES

d. Is there friction? NO!

Fg

Fa

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UNIT 2

FORCE PROBLEMS

EASY – NO ANGLES

EVERY FORCE IS EITHER PARALLEL TO

THE X AXIS OR PARALLEL TO THE Y AXIS

FORCESEXAMPLE 1

1. You are attempting to move a box of cats

across the ground. If the box has a mass of

14kg, and the coefficient of static friction is

0.68, how much force must you apply to move

the box? You must apply at least

93.30 N of force to move

the box.

FORCESYOU TRY

2. You are moving a box of puppies across the

ground with a force of 100N. If the box has a

mass of 23kg, and the coefficient of kinetic

friction is 0.33, what is the acceleration of the

box? The box of puppies has an

acceleration of 1.11 m/s2

in the x direction.

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MEDIUM– FORCES AT ANGLES

AT LEAST ONE FORCE IS ACTING AT AN

ANGLE

YOU HAVE TO USE SOH CAH TOA TO FIND

THE X AND Y COMPONENTS OF THE

FORCE AT AN ANGLE

FORCESEXAMPLE 2

You are moving a box of turtles across the

ground with a force of 100N at an angle of 34

degrees. If the box has a mass of 15kg, and

the coefficient of kinetic friction is 0.24, what

is the acceleration of the box?The box of turtles has an acceleration of

4.07 m/s2 in the x direction.

FORCESYOU TRY

4. You are moving a box of turtles across the

ground with a force of 150N at an angle of 27

degrees. If the box has a mass of 10kg, and

the coefficient of kinetic friction is 0.36, what

is the acceleration of the box?The box of turtles has an acceleration of

12.29 m/s2 in the x direction.

𝐹𝐺 = 𝐺𝑚1𝑚2

𝑟2

Law of Universal

Gravitation (Attraction)

F = the force between the masses

G = 6.67 x 10-11 N*m2/kg2

m1 = is the first mass,

m2 = is the second mass, and

r = the distance between the centers of the masses

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5 Question Quiz

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