BF and UF 2

• Physics
• Secondary Education
• Age 13

Forces and Motion

Lesson 01. Forces

How are you today?

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Highlights of the Day

• describe the effects of balanced and unbalanced forces on motion

• Value :  Responsibility

Forces and Motion

Lesson 01. Forces

What is a "force"?

QUESTION TIME!

Forces and Motion

Lesson 01. Forces

Can you see the forces acting on an object?

YES

NO

Can you see the EFFECTS of forces acting on an object?

YES

NO

If you cannot see force, 

how can you show it in a diagram?

Using an arrow

tail

head

}

length

Forces have magnitude and direction.

stronger

weaker

The ball is at rest or not moving. What forces are acting on the ball?

Forces acting on the ball

weight by gravity

Forces acting on the ball

weight by gravity

normal force

If mass has a unit of grams, which of the following is the unit of force?

1. kilograms (kg)
2. newtons (N)
3. meters (m)

Positive and Negative Directions

Positive Directions

Negative Directions

Forward

North

Backward

South

right

left

down

up

What type of direction is "rightward"?

1. negative
2. positive
3. meters (m)

Unit of FORCE

newtons  or  N 

Forces acting on the ball

weight by gravity

normal force

Example 1:

normal force

positive 10 newtons ( + 10 N)

upward is POSITIVE

Example 2:

weight by gravity

negative 10 newtons ( - 10 N)

downward is NEGATIVE

Forces acting on the ball

weight by gravity

normal force

+5 newtons

-5 newtons

Force Diagram

weight by gravity

normal force

+5 newtons

-5 newtons

wind

wind

How will you make the ball move?

-3 newtons

+3 newtons

force 1

force 2

Balanced forces are two or more forces acting on an object that are ______ in size and _______ in direction.

1. unequal ; opposite
2. equal ; opposite
3. unequal ; similar
4. equal ; similar

Forces and Motion

ACTIVITY 27.1. Diagram Me!

Rate your level of understanding and participation in this lesson.

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