Question

A lever of length 9 cm has its load arm 5 cm long and the effort arm is 9 cm long.

1. To which class does it belong?
2. Draw a diagram of the lever showing the position of fulcrum F and directions of both the load L and effort E.
3. What is the mechanical advantage and velocity ratio if the efficiency is 100%?
4. What will be the mechanical advantage and velocity ratio if the efficiency becomes 50%?

Answer 1

1. 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.
2. 
   

3. 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

4. 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`