1. Properties of a machine
Machines 1
Machines
Next Slide
Properties of a machine
Transfer energy from one place to another place
Change the direction of a force
Change the magnitude of a force
Can never change the magnitude of energy
Examples
Diagram

2. Terms related to a machine
Machines 2
Machines
Next Slide
Terms related to a machine
Effort (the force we apply to the machine)
Load (the force that the machine supplies to move the desired object
Input energy = work done by the effort = effort  distance moved by the effort
Output energy = work done on the load = load  distance moved on the load

3. Terms related to a machine
Machines 3
Machines
Next Slide
Terms related to a machine
Calculation
Since output energy is always smaller than input energy, the efficiency is always smaller than 100 %.
Loss energy may become sound and internal energy due to friction or be used to increase the P.E. the movable part of the machine.

4. Various kinds of machine
Different Machines 1
Machines
Next Slide
Various kinds of machine
A machine which enables a heavy load to be raised by a small effort, is a force multiplier..
Various kinds of lever : nut cracker, scissors, single-wheel cart
Diagram
Inclined plane
Calculation
Wheel-and-axle
Calculation

5. Various kinds of machine
Different Machines 2
Machines
Next Slide
Various kinds of machine
Screw-jack
Calculation
Hydraulic press
Calculation
Single pulley
Calculation
Gears
Bicycle
Calculation

6. END of Machine

7. Machines 1 Machines Next Slide
Transfer energy from one place to another
energy
Change the direction of a force
tension
upwards
pulling force
downwards

8. Back to Machines 1 Machines Click Back to
Change the magnitude of a force
heavy
load
small effort

9. Machines 3 Machines Next Slide
By making use of a lever, an effort 20 N is used to raise a block (mass 5 kg) by 5 cm as shown in the following diagram. What is the efficiency of this lever? How much energy has been lost?
20 N
mass : 5 kg
5 m
1 m
pivot

10. Machines 3
Machines
Next Slide
effort
1 m
pivot
5 m
0.25 m
0.05 m

11. Back to
Machines 3
Machines
Click Back to

12. Different Machines 1 Machines Next Slide Nut Cracker load effort pivot
Scissors
effort
load
pivot
paper

13. Back to Different Machines 1 Machines Click Back to Single-wheel cart
load
effort
pivot
sand

14. Different Machines 1 Machines Next Slide
A block (mass 20 kg) is pulled by a force 100 N upwards along the incline plane shown. Find the efficiency of the machine and the friction acting on the block by the plane.
5 m
2 m
rough incline plane
100 N

15. Back to
Different Machines 1
Machines
Click Back to

16. Different Machines 1 Machines Next Slide
2 kg of water is raised in a bucket with mass 0.5 kg by a wheel-and-axle machine as shown in the following figure. Assume that the handle has been turned by an effort 10 N for one round, find its efficiency.
0.3 m
0.1 m
10 N
water 2 kg
bucket 0.5 kg

17. Back to Different Machines 1 Machines Click Back to
In this case, only the water is considered as the load. The bucket is thought as one part of the machine. Therefore, when we consider the energy gained by the load, we only consider the P.E. gained of the water.

18. Different Machines 2 Machines Next Slide
A screw jack is used to raise the load (mass : 1000 kg) by an effort 50 N as shown in the following figure. The height of the pitch is 1 mm and the length of the handle is 0.5 m. Find its efficiency. Such an machine needs a LOW efficiency, why?
Load :1000 kg
0.5 m
height of
pitch : 1 mm
Effort :
50 N

19. Back to Different Machines 2 Machines Click Back to
Assume that the handle has been turned for one round. The load would be raised by a height equal to the height of pitch.
Small efficiency means the energy lost due to friction is large. Therefore, the friction of this machine is very large. If we remove the effort, the friction is large enough to prevent the load from falling downwards.

20. Different Machines 2 Machines Next Slide
A hydraulic press is used to move a load (mass : 100 kg) upwards for 1 cm as shown. The distance pushed by the effort 20 N is equal to 1 m (Why?). Find its efficiency.
oil
1 m
1 cm
effort 20 N
load 100 kg

21. Back to Different Machines 2 Machines Click Back to
It is very difficult to compress oil. Therefore, the volume of oil transferred to the column with the load remains the same.

22. Different Machines 2 Machines Next Slide
A fixed pulley is used to move an load 20 kg upwards by an effort 250 N. The load has been raised by a height 1 m. Find its efficiency.
load : 20 kg
effort : 250 N

23. Back to Different Machines 2 Machines Click Back to
The tension in the string holding the load is not equal to 250 N. It was because there is friction between and the string and the pulley.

24. Different Machines 2 Machines Next Slide
A bicycle has the following dimensions:
Find the distance moved by pedal and the wheel respectively if the crank has been turned for one round. Do you think that this machine is a force multiplier?
0.50 m
0.25 m
18 teeth
36 teeth

25. Back to Different Machines 2 Machines Click Back to
In this case, the distance moved by the effort (pedal) is much shorter than the load (bicycle). Therefore, it is not a force multiplier.
Bicycle is a machine that cannot save force. However, it can greatly increase the distance moved.