A lift starts from rest and begins to descend such that its downward acceleration varies with time as a=2tms−2, where t is in seconds (t≥0). A block of mass 5kg is kept on a spring balance inside the lift.
(i) Write an expression for the reading R(t) of the balance at an arbitrary time t. Assume g=9.8ms−2.
(ii) At what time will the balance first read zero?