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Question
A lever of length 9 cm has its load arm 5 cm long and the effort arm is 9 cm long.
- To which class does it belong?
- Draw a diagram of the lever showing the position of fulcrum F and directions of both the load L and effort E.
- What is the mechanical advantage and velocity ratio if the efficiency is 100%?
- What will be the mechanical advantage and velocity ratio if the efficiency becomes 50%?
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Solution
- The length of the lever is the same as the effort arm. Also, an effort arm is more than a load arm. So, this is a class II lever.
-
Mechanical advantage is
M.A. = `"effort arm"/"load arm" = (9 "cm")/(5 "cm")`
= 1.8
The relationship between MA, efficiency and V.R. is
M.A. = η × V.R.
V.R. = `(M.A)/η`V.R. = `(1.8 xx 100)/100`
V.R. = 1.8
-
When efficiency becomes 50%, i.e.,
`50/100 = 1/2`
M.A. < V.R.
Then V.R. will remain same 1.8
but its M.A. will become
M.A. = V.R. × η
M.A. = `(1.8 xx 50)/100 = 0.9`
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