A boy uses a single fixed pulley to lift a load of 50 kgf to some height. Another boy uses a single movable pulley to lift the same load to the same height. The ratio of the two effort is:

1. 1:2
2. 2:1
3. 1:1
4. none of these

How many strands are supporting the load in case of block and tackle system of 5 pulleys?  

1. 4
2. 5
3. 6
4. 7

For a system of n pulleys, the weight of the lower block along with pulleys is w, then its efficiency is given by:

1. $\eta = 1 - \dfrac{w}{nE}$
2. $\eta = 1 + \dfrac{w}{nE}$
3. $\eta = \dfrac{w}{nE}$
4. $\eta = n - \dfrac{w}{E}$

Assertion (A): The mechanical advantage of class III levers is always less than 1.

Reason (R): This is because the effort arm is always greater than the load arm.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true and R is not the correct explanation of A.
3. assertion is false but reason is true.
4. assertion is true but reason is false.