A student pulls a suitcase by its handle while walking along a straight airport corridor. The handle makes different angles with the horizontal during the journey.
(i) For each of the following angles between the pulling force and the horizontal displacement—0∘, 90∘ and 120∘—state whether the work done by the pulling force is positive, zero or negative, giving a brief reason in each case.
(ii) Explain why, for the same magnitude of pulling force, a small acute angle makes it easier to move the suitcase than a large obtuse angle.