Force And Pressure

How to teach force & pressure and it's misconceptions

1. FORCE AND PRESSURE

2. RELATIONSHIP
BETWEEN FORCE
AND PRESSURE
FRICTION
EFFECTS OF
FORCE
INTRODUCTION
FORCE

3. - playing a guitar - scrubbing the floor
- sawing wood - rowing a boat
• A pull is when we apply a force to
move an object towards our body
• A force to move an object away from
our bodies
FORCE
A force is a push or a pull or both. A force cannot be seen but we can feel and
observe the effects of the force.
PUSH
PULL
COMBINATION OF PUSH AND PULL

4. Pressing the switch
Kicking a ball
Launching rocket
Pushing trolley
Knocking a
nail

5. Tug-of-war
Raising a flag
Pulling a box
Opening the door
Drawing back a bow

6. Rowing a boat
Scrubbing the
floor
Sawing wood
Playing guitar

7. Stops a moving
object or makes a
stationary object
moves
Change the
speed of a
moving object
Change the
direction of a
moving object
Changes the
shape
permanently
Changes the
shape
temporarily
EFFECTS OF
A FORCE

8. Stretch a rubber bandStretch a rubber band
After
An object that will return to its original shape and size after being
squeezed, pressed, twisted and stretched is elastic
After After
Press a spongePress a sponge Squeeze a springSqueeze a spring

9. Drop a glassDrop a glass
After
After
Tear a piece of paperTear a piece of paper
After
Crush an empty canCrush an empty can
An object that will not return to its original shape and size after being squeezed,
pressed, twisted and stretched is inelastic
MISCONCEPTION???

10. A solid cannot be compressed or stretched!!
CHILDREN’S MISCONCEPTIONCHILDREN’S MISCONCEPTION
EXPLANATIONEXPLANATION
The shape of a solid object changes when a force is
applied to it whether it’s temporarily or permanently
Example: crushing a can – changes the shape

permanently

11. when a force is applied in
the opposite direction
(or different direction), the
moving object will change
its moving direction
MISCONCEPTION???

12. Misconception?
A force is needed to keep an object moving with a constant speed
Explanation:
You do not need forces to move at a steady speed but if you keep the same
speed yet change direction, like a moon around a planet, then you have a
force acting on you anyway
An object will move faster when
a force is applied
It moves in the same direction as
the applied force

13. • A stationary ball will move when it is
kicked
• Moves in the same direction as the
applied force
•The moving ball will stop when
an equal force is applied in the
opposite direction of its motion
MISCONCEPTION???

14. Force is a property of an object. An object has force
and when it runs out of force it stops moving
EXPLANATIONEXPLANATION
an object at rest or in motion will
remain in that state unless an
external force is applied to the
object
Newton 1
st
Law

15. FRICTION
- Occurs when two
surfaces are moving
in contact with each
other
Factors that effect
friction
Physical condition
of the surface
Weight of
an object
Advantages
• enables people to run and walk
without falling or slipping
• enables us to write on paper
• enables a car to stop when the brakes
are applied
• enables an object to be stationary
• music instruments can produce sound
• allows vehicles to travel on the road
without slipping
Disadvantages
• slows down a moving object
• causes the surfaces of objects
to wear out
• causes less effectiveness of
moving machine
• causes heating
• causes sound pollution
• increases cost when worn-out
objects need to be replaced
with new ones
Ways to reduce
• use ball bearing
• use wheel and axle
• use lubricants such as grease
or oil
• use air cushion
• use roller bearing

16. MISCONCEPTION???
Friction is only present when something is
rubbing against a moving object
EXPLANATIONEXPLANATION
Occurs when two surfaces are moving in contact
with each other

17. Examples of friction

18. RELATIONSHIP BETWEEN FORCE AND
PRESSURE
•AIR PRESSURE
BICYCLE PUMP
A force is applied to the pump to
produce air pressure
Applying
force
Pull and push