The mechanical advantage of a machine is __________.

• A. the input force divided by the output force
• B. the distance the input moves divided by the distance the output moves
• C. always greater than or equal to 1
• D. the distance the output moves divided by the distance the input moves

Answer: (B)

The key idea is that a machine swaps distance for force. In an ideal machine, work in equals work out, so F_in × d_in = F_out × d_out. If you rearrange that, you get d_in/d_out = F_out/F_in. That means the mechanical advantage can be seen as either the ratio of output force to input force or, equivalently, the ratio of input distance to output distance.

The statement about the input distance moved divided by the output distance moved matches that second view, so it correctly describes mechanical advantage.

The other possibilities either invert the ratio or use the reciprocal distance, and one option claims MA is always ≥ 1, which isn’t true when considering real machines with losses or certain configurations.