The diagram in Figure shows the combination of two pulleys P_(1) and P_(2) used to lift up a load W. (a) State the kind of pulleys P_(1) and P_(2). (b) State the function of the pulley P_(2). (c) If the free end C of the string moves throughadistance x, by what distance is the load W raised ? (d) What effort E has to be applied at C to just raise the load W=20 kgf ? Neglect both the weight of the pulley P_(1) and friction.

The diagram in Figure shows the combination of two pulleys P_(1) and P

1.	The diagram in Figure shows the combination of two pulleys P_(1) and P_(2) used to lift up a load W. (a) State the kind of pulleys P_(1) and P_(2). (b) State the function of the pulley P_(2). (c) If the free end C of the string moves throughadistance x, by what distance is the load W raised ? (d) What effort E has to be applied at C to just raise the load W=20 kgf ? Neglect both the weight of the pulley P_(1) and friction.
Answer» Solution :(a) `P_(1)` is the movable pulley while `P_(2)` is the fixed pulley. (b) The fixed pulley `P_(2)` is used to CHANGE the direction of effort to be APPLIED, from upward direction to DOWNWARD direction. (c) If the free end C of the string moves through a distance x, the load W will rise by a distance x/2. (d) Given W=20kgf, E=? In EQUILIBRIUM, W=2T and E=T `therefore` Effort needed E=`(W)/(2)=(20kgf)/(2)=10kgf`.