Question

A courier is delivering a 5kg package to an office high in a tall building.

(a) What upwards force does the courier apply to the package when carrying it horizontally at a constant velocity of 2m/s into the building?

(b) The courier uses the elevator to reach the office. While the elevator (containing the courier who is holding the package) is accelerating upwards at 0.11m/s what upwards force is the courier applying to the package?

(c) When the elevator is travelling upwards at a constant speed of 6m/s what upwards force does the courier apply to the package?

(d) In order to stop at the correct floor the elevator accelerates downwards (decelerates) at a rate of 0.20m/s. What is the upwards force the courier applies to the package during the deceleration?

Answer 1

a. upward force equals the weight of the package, of course, mg
b. upward force equals weight plus accelerating force, mg+ma
c. same as b, but a is zero.
d. same as b, but a is now negative.