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# SIMPLE MACHINES

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by

## Teh Ren Jie

on 1 October 2013

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#### Transcript of SIMPLE MACHINES

SIMPLE MACHINES
10.1 Levers
Machine - Device which helps to make our work easier
FIRST CLASS LEVERS
The fulcrum is located between the effort and load.
SECOND CLASS LEVERS
The load is located between the fulcrum and the effort
THIRD CLASS LEVERS
The effort is between the fulcrum and the load
PRINCIPLE OF LEVERS (MOMENTS)
The principle of levers states that when a lever is in equilibrium, the product of load and distance of load from the fulcrum is equal to the product of effort (force) and the distance of effort from the fulcrum
Lever - Simple machine that consists of a stiff rod that can turn freely about a fixed point called the fulcrum (F) when a force called effort (E), acts to overcome another force called the load (L)
Effort and load acts in the same direction
A small effort can move a large load
However, the effort has to be closer to the fulcrum compared to the load.
Effort
Fulcrum
The load and effort act in different directions
A small effort can lift a large load
The effort is always farther from the fulcrum compared to the load
Effort
Fulcrum
The effort and the load act in opposite directions
The effort acts at a point closer to the fulcrum than the load
Thus, a large effort can only lift a small load
This lever is used to make work easier, not to ease work done
Effort
Fulcrum
Effort (N) x Distance of the effort
When the distance of effort is greater than the distance of load, then the magnitude of effort is less than that of the load.
Effort
Fulcrum
Distance of effort
Distance of effort
Fulcrum
Effort
Distance of effort
Effort
Fulcrum
1ST CLASS LEVER
2ND CLASS LEVER
3RD CLASS LEVER
QUESTIONS
#1
Define first class levers and state two examples.
#2
State the formula of the principle of moments
#3
Calculate the magnitude of effort needed on the rod shown in the diagram below to keep it horizontal.
#4
Label this simple machine correctly
Define second class levers and state two examples
Define third class levers and state two examples
How do you make work easier?
effort
10cm
30cm
15N
Examples
Examples
Examples
EXAMPLE
How to solve problems related to levers??
Aha!
Question
5N
15cm
Effort
Fulcrum
30cm
How much effort must be exerted to enable the rod to be in equilibrium?
Solution
Write down the formulae for the principle of moments, i.e.,
Substitute it with the relevant values.
5N x 30cm = Effort x 15cm
Solve the problem to get the answer.

Effort = (5N x 30cm) / 15cm
= 150N / 15
= 10N
Credits
Teh Ren Jie
Neoh Woei Shuen
Wisely Koay Zhi Tang
Khoo Kai Jun
THANK
YOU
MOMENT OF FORCE
A force multiplied by its lever arm
The turning effect of a force about a fulcrum
Moment of a force =
Force x Perpendicular distance of the force
The unit of the moment of force is Nm (Newton metres)
Full transcript