A rocket rises vertically from the ground. During the first 10s its engines produce a constant upward acceleration of 5.0ms−2 relative to the ground. The engines then cut off, after which the rocket moves only under the influence of gravity until its downward journey brings it past the launch point.
A block of mass 4.0kg is placed on a spring balance fixed to the floor of the rocket.
(i) Find the reading of the balance during the powered ascent.
(ii) Determine the reading immediately after engine cut-off, while the rocket is still moving upward.
(iii) What will the balance read while the rocket is falling back past the launch point (before air drag or parachutes act)?
(iv) Explain physically why the readings obtained in parts (ii) and (iii) differ from that in part (i).