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Introduction to Forces & FBDs

Introduction to Forces & FBDs

Assessment

Presentation

Physics

12th Grade

Practice Problem

Easy

NGSS
MS-PS2-4, MS-PS2-1, HS-PS2-1

+1

Standards-aligned

Created by

Ms. Das

Used 30+ times

FREE Resource

15 Slides • 10 Questions

1

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Forces and Free Body

Diagrams

2

Multiple Choice

The unit for Force is

1

meters

2

Newton

3

meters per second

4

meters per second squared

3

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What is a Force?

A force is a push or a pull on an object resulting from the interaction
of the object with something else

2 types of forces - contact forces and at-a-distance forces

Contact Forces

Frictional Force

Tension Force

Normal Force

Air Resistance Force

Applied Force

Spring Force

At-a-Distance Forces

Gravitational Force

Electrical Force

Magnetic Force

4

Categorize

Options (8)

friction

gravitational force

tension

normal force

magnetic force

applied force

air resistance

electrical force

Organize these options into the right categories

Contact force
NonContact Force

5

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Unit of Forces

Force is measured in Newtons
Newtons are equal to 1 kg*m/s2

Forces are a vector, meaning they have a magnitude AND

direction

Forces can be represented in pictures by drawing vectors

These drawings are called free-body diagrams

6

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Gravitational Force

Attractive force between two objects

On earth, gravity is always directed
downward

Gravitational force is also called
weight

Fg = m*g

m = mass

g = acceleration of gravity

g on earth is always -10 m/s2

7

Multiple Choice

Which of the following statements about gravitational force is FALSE

1

It is measured in Newtons

2

It always points down towards the Earth

3

It is also known as mass

4

It is also known as weight

8

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Normal Force

The force that is exerted on an object
in contact with a surface

When two objects are in contact with eachother, they each exert a Normal Force on the other

Normal force is always in the direction
perpendicular to the surface

9

Multiple Choice

Question image

The picture shows an individual leaning against a wall. Which of the following correctly describes the normal force acting on the person? Select TWO answers.

1

The person is pushing the wall to the left

2

The wall is pushing the person to the right

3

The ground is pushing the person upwards

4

The Earth is pulling the person downward

10

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Applied Force

This is simply any force
applied to an object

Examples:

Pulling a desk across
the room

Pushing a ball down a
ramp

11

Open Ended

Give two examples of an applied force not mentioned in the previous slide.

12

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Tension

Force exerted by a rope, string,
cable, chain, etc.

Tension only occurs when rope,
chain, etc. is pulled taut and has
forces acting on both ends

When objects are hanging directly
downward, tension will equal
gravitational force and be directed
upward

13

Dropdown

Question image
The picture shows a birdfeeder hanging from a tree in my backyard. The direction of the tension force on the birdfeeder is . . . . ​

14

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Frictional Force

The force a surface exerts on an object
that resists the object’s motion

Frictional force will most often be
opposite direction of the object’s
movement

The closer an object is to a surface, or
the more firmly pressed down it is to the
surface, the higher the frictional force is

Friction can be found using:
Ffrict = µ • Fnorm

15

Drag and Drop

Drag all of the TRUE statements to the empty boxes shown here: ​
​ ​


Drag these tiles and drop them in the correct blank above
friction acts parallel to a surface
friction is measured in Newtons
friction opposes motion
friction always points left or right
friction is measured in meters

16

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17

Dropdown

If an object has no air resistance force acting on it, and only has gravitational force acting on it, we say that the object is in FREE FALL​

18

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19

Multiple Choice

Question image

What type of force is the BLUE arrow indicating?

1

Applied Force

2

Gravity

3

Friction

4

Normal Force

20

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Checkpoint!
Practice

A flying squirrel is gliding
(no wing flaps) from a tree to
the ground at constant
velocity. Consider air
resistance. Diagram the
forces acting on the squirrel.

21

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Checkpoint!
Practice Continued

An egg is free-falling from a
nest in a tree. Neglect air
resistance. Diagram the forces
acting on the egg as it is falling.

22

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Checkpoint!
Practice Continued

A gymnast holding onto a bar,
is suspended motionless in
mid-air. The bar is supported by
two ropes that attach to the
ceiling. Diagram the forces acting
on the combination of gymnast
and bar.

23

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Checkpoint!
Practice Continued

A rightward force is applied to a
book in order to move it across a
desk with a rightward acceleration.
Consider frictional forces. Neglect
air resistance. Diagram the forces
acting on the book.

24

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What do Net Forces mean for motion?

A Net Force simply means that the forces on the object

are unbalanced

If an object has a Net Force, it is accelerating
Net forces, just like regular forces, are a VECTOR and

have a DIRECTION

25

Multiple Choice

Question image

The net force acting on the box shown in the picture is

1

600 N up

2

13 N right

3

637 N

4

13 N left

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Forces and Free Body

Diagrams

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