1. SIMPLE MACHINES

2. RECAP
A force is any action that changes or tends to change the size, shape and/or state of rest/motion of a body.
A force is NOT a matter. It has NO mass and does not take up space.
We define force as a push or a pull.

3. SI unit for force is Newton (N).
We can see effects of forces everyday in our daily lives eg, compressed, stretched, bent or twisted.

4. LEVER
A simple machine that turns about a fixed point (F) when a force (E) is applied to move another force (L).

5. Levers help us to do work by
Reducing the effort needed to overcome a load
Producing a large movement from a small movement.

6. applied force
LOAD
EFFORT
FULCRUM
fixed point

7. How does lever make work easier?
Using small effort to overcome a bigger load.
An example is the see-saw

8. To overcome a load with less effort.
Effort should be as far away as possible from the fulcrum.
load
Effort
fulcrum

9. To overcome a load with less effort.
Load should be as near as possible to the fulcrum.
load
Effort
fulcrum

10. Small effort, Big load
fulcrum
Distance moved by the effort is MORE than the distance moved by the load.
load
distance
effort

11. Big effort, Small load
a small movement of the effort causes a large movement of the load.
Greater amount of effort needed to move the load.
load
effort
fulcrum

12. Question! Which position require a bigger effort? What does represent?
Position A
Position B
effort
effort
Which position require a bigger effort?
What does represent?
What if is moved nearer to the load?

14. INCLINED PLANES
A slanted surface that joins two different levels.

15. Inclined planes help us to do work by
Reducing the effort needed to move a heavy load.
BUT!
Effort will have to move through a longer distance.

16. Distance moved by effort when box is lifted vertically.
load

17. Distance moved by effort along the plank
load

18. Examples of inclined planes
ladder
slide
stairs
ramp

19. Questions! A B D C

20. What kind of simple machine is a ramp? It is a lever
What is the advantage of using ramp B?
It will need the least effort to move the load.
What is the advantage of using ramp D?
The load will travel the shortest distance.
What is the difference between A and C?
A is inclined at a smaller angle than C.
How can we convert a plank into a ramp?
By supporting a plank at an angle. A C B D

21. PULLEYS
A wheel with a groove where a rope can go over. It is used for lifting objects.

22. What is a pulley?
A pulley is a wheel with a groove where a rope or string can go over.
Fixed pulley
Movable pulley
Pulley system

23. FIXED PULLEY A pulley in a fixed position. Eg : flag pole.
It does not reduce the effort used to lift a load.
It makes work easier by changing the direction of the applied force (effort).

24. MOVABLE PULLEY Not a fixed pulley
Can be used to lift an object with a smaller effort.
BUT!
Effort has to move through a longer distance than the load.
DOES NOT change direction of the applied force.

25. PULLEY SYSTEM Combines the fixed pulley and the movable pulley.
Direction of the force is changed
A smaller effort is needed to raise a heavy load.