State whether the following statements are true or false:

(a) A boy does work while pushing a wall.

(b) A machine performs work by itself.

(c) In an ideal machine, work done on load is equal to the work done by effort.

(d) All levers are force multipliers.

(e) A pulley changes the direction of force.

(f) An inclined plane always has the mechanical advantage more than 1.

(a) False because work is said to be done if the force applied on the body moves it. If no motion or change in position takes place, no work is said to be done so when a boy pushes a wall, no work is done by him since wall remains stationary.

(b) False because a machine can do useful work only when energy is supplied to it; it cannot work by itself.

(c) True because a machine in which no part of the work done on the machine is wasted, is called an ideal or perfect machine. Thus, for an ideal machine, the work done on load is equal to the work done by effort.

(d) False as Class I and Class II levers can act as force multipliers when the effort arm is longer than the load arm, but Class III levers have the effort applied closer to the fulcrum and thus do not multiply force.

(e) True because a pulley is a simple machine by which the direction of effort is changed to raise up a load.

(f) True because the effort required to push a load up an inclined plane is less than the load. Thus, the mechanical advantage of an inclined plane is always greater than 1.