Which of the following statements is incorrect? (a) For a machine, velocity ratio does not change. (b)Due to friction, mechanical advantage of a machine increases. (c) For an ideal machine, work output is equal to the work input. (d) For an ideal machine, mechanical advantage is numerically equal to the velocity ratio

(b) Due to friction, the mechanical advantage of a machine increases.

Reason — Friction reduces the mechanical advantage of a machine because frictional forces oppose motion, which means they can decrease the efficiency of a machine by dissipating energy as heat. This results in a decrease in the mechanical advantage of the machine.