5. A little boy tries to push a heavy cupboard. He uses a force of 400 N, but he is unable to move the heavy cupboard.
(a) How much work has he done?
(b) Explain your answer in (a).
(c) For work to be done, the following conditions must be satisfied:
(i) There must be a
acting on the object.
(ii) The object must
in the direction of the force.

Which type of circuit is becoming more common in residential electrical design and construction? a. hazardous-area circuit b. three-phase circuit c. 480-volt circuit d. communication circuit

Aparticle's position is given by x = 3.00 - 9.00t + 3t2, in which x is in meters and t is in seconds. (a) what is its velocity at t = 1 s? (b) is it moving in the positive or negative direction of x just then? (c) what is its speed just then? (d) is the speed increasing or decreasing just then? (try answering the next two questions without further calculation.) (e) is there ever an instant when the velocity is zero? if so, give the time t; if not, answer "0". (f) is there a time after t = 3 s when the particle is moving in the negative direction of x? if so, give the time t; if not, answer "0".

How can waves travel through ground?