Question

The diagram shows an arrangement of three pulleys $A,B$ and $C$. The load is marked as $L$ and the effort as $E$. How are the magnitudes of $L$ and $E$ related to the tension $T_1$?

• A. $L=T_1,E=T_1$
• B. $L=T_1,E=4T_1$
• C. $L=4T_1,E=4T_1$
• D. $L=4T_1,E=T_1$

Answer 1

The correct option is D $L=4T_1,E=T_1$

The unknown forces, L and E, can be calculated by putting net force equal to zero on each pulley.

Let's start with pulley C:

The tension in the string will be equal to E, because a string always has equal forces on the both end if the pulley is frictionless.

$E=T_1$

On pulley B:

$T_2=2T_1......equation1$

On pulley A:

$L=2T_2......equation2$

By putting value of $T_2$ from equation 1 to equation 2

$L=2\left(2T_1\right)$

$L=4T_1$