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# Mechanical Efficiency

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## Nicholas Chew

on 11 December 2013

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#### Transcript of Mechanical Efficiency

Mechanical Efficiency
EQs- Essential Question
- What is mechanical efficiency?
- How is mechanical efficiency used?
Vocabulary
Expenditure- It is the action of spending energy.
Mechanical Efficiency- The numerical representation that measures the effectiveness of a machine.
Force- Force is the cause of objects moving.
M.E... How is it used?
Mechanical efficiency is used in:
- Set constructions
- People use engines to reduce the time and the amount of work they have to do.

Example: A crane helps humans to carry heavy objects which makes the job much easier.
Some Notes on Mechanical Efficiency... Output!
Mechanical efficiency is the measure of effectiveness of a machine's energy and power that is input into the device into an output that makes force and movement.
Mechanical advantage by comparing the input and output force you can find the advantage of a machine.
- Increased force is when the output force is bigger than the input force.
- The mechanical advantage of a machine is bigger than 1.
- Increased distance is a machine that increases its distance. The output force is lower than the input force, that means that the mechanical advantage is lower than 1.
The "Machine Efficiency"
- In every machine little work is wasted while trying to overcome the force of friction.
- To calculate the mechanical efficiency, divide the output work by the input work, then you have to multiply it by 100.
Force
- The cause of objects moving is, Force.
- Force can even make an object change direction, and even make the object stop.
Quiz Time!
Q1. What is the definition of mechanical efficiency?
Q2. What is the formula for mechanical efficiency?
a) F=ma
b) Output force/input force
c) Output force/input force x 100

Q3. What is force?
Q4. What is expenditure?
a) The action of spending energy.
b) Going to the shop to buy a pony.
c) The numerical representation of the effectiveness of a machine.

Q5. One example of how mechanical efficiency is used:
Q6: What is the formula of mechanical advantage?

Example Questions and Scenarios:
- How do we use M.E.?

- A person is putting a cassette from a bike into a bucket of oil to reduce the amount of friction.

- Changing all of your light bulbs to energy efficient ones reduces energy use and the light bulbs last.
Equation for Calculating mechanical efficiency: (P-Pf)/P
Please Pay Attention! QUIZ after presentation!
IMPORTANT
P- Represents power transferred
Pf- Represents power lost in transmission.
Thank you All for your Attention!
Real and Ideal Efficiency?
Quiz Time!
- Ideal machines have a efficiency of 100% but unfortunately there isn't any machines like that in the whole world.
Ideal Machines
Real Machines
- Real machines have an efficiency below 100% as some work is wasted to friction
Examples of Calculating Mechanical Efficiency and Mechanical Advantage!
If your output force is 40 newtons, and your input force is 80 newtons, what is the mechanical advantage?
40/80= 0.5
Output Force/ Input Force.
Mechanical Efficiency
Formula For Mechanical Efficiency-
Output Force/ Input Force x 100
If your work input is 100N, and your work output is 600N, what is the mechanical efficiency?
600/100= 6
6 x 100= 600
Difference Between Mechanical Efficiency and Mechanical Advantage
Mechanical advantage is the number of times a machine increases the input force while mechanical efficiency is the ratio of output work to input work.
Guided Practice- With teacher.