FORCE

This is HEAVY!

I can’t hold it

anymore!

Can someone help

me?

FORCE

• push or pull

• object’s interaction with its

environment

• vector quantity

• unit is Newton

NET FORCE

• the sum of all the forces acting on

the object.

• a physical quantity that is capable of

changing an object’s state of motion

5 N3 N 3 N

5 N

Net force = 2N, right Net force = 8N, right

Four Fundamental Forces

1. Gravitational Force

– Force of attraction between two masses

Position of the stars and

planets

2

21

r

mmGFg

2. Electromagnetic Force

Force that affects charge particles

Your hair will be attracted to

a charged balloon

The electrons from the

clouds will travel towards

the land - thunderbolts

3. Weak Nuclear Force

4. Strong Nuclear Force

Four Fundamental Forces

Radioactive decay

Binds proton in the

nucleus

Forces acted on an object

1. Weight

- gravitational attraction of an

object and the earth

- always directed downwards

- W = mg

weight

Normal

force

2. Normal Force- support force exerted upon

an object

- perpendicular to surface

Forces acted on an object

3. Applied force

- force applied simply by

pushing or pulling

weight

Normal

force

Applied

force

Friction

4. Friction

- force exerted by a surface as

an object moves across it

- parallel to surface and

opposite to the direction of

motion

Forces acted on an object

5. Tension

- force which is transmitted through

a string, rope, cable or wire when it

is pulled tight by forces acting from

opposite ends.

T

e

n

s

i

o

n

6. Air resistance

- force exerted by the air as an

object moves in it

- opposite to the direction of

motion

Newton’s

Law of Motion

1. Law of inertia

2. Law of

Acceleration

3. Law of Interaction

I have answer to

your inquiry

Law of Inertia

The body at rest tends to remain at rest,

and a body in motion continues to move

at constant velocity unless acted upon

by a net force.

Inertia is the property of a body which

resists any change in its state of rest or

motion.

Inertia is proportional to mass.

Importance of using Seatbelts

Importance of Seatbelts

Seatbelt exerts force on

the person for him not

to move forward when

it suddenly stops.

Force

(seatbelt)

Try This at Home

Egg Drop Challenge

Law of

Acceleration

The acceleration of an

object depends directly

upon the net force acting

upon the object, and

inversely upon the mass of

the object.

Law of Acceleration

Acceleration is directly proportional to mass

Acceleration is directly proportional to mass

a F

a 1/m

a = F/m

Law of Acceleration

maForm

Fa

Force (N) Mass (kg) Acceleration (m/s2) Your answer is...

20 ? 2 Try again

15 3 ? Try again

? 0.9 3 Try again

30 ? 0.5 Try again

0.6 0.2 ? Try again

? 20 10 Try again

Law of

Interaction

For every action,

there is an equal and

opposite reaction.

Law of Interaction

You push

the wall

by 50 N

The wall

push you

by 50 N in

the

opposite

direction

Action

Reaction

Law of Interaction

Action Reaction

You push the ground

downward

The apple is pulled by

the Earth downward

The rocket exhausts

gas to the ground

downward

The ground will push

you upward

The Earth is pulled by

the apple upward

The gas will push the

rocket upward