Question

A lift ascends with constant acceleration $a=1m{s}^{-2}$ , then with constant velocity and finally, it stops under constant retardation $a=1m{s}^{-2}$ . If total distance ascended by the lift is $7m$ , in a total time of the journey is $8s$ . Find the time (in second) for which lift moves with constant velocity.

Answer 1

Answer: 6

$a=\frac{v}{t_1}$


$t_1=\frac{v}{a}$ ...(i)
$t_0=8-2t_1$ ...(ii)
$s_0=7-2s_1$ ...(iii)
Solving equation (i), (ii) and (iii), we get
$t_0=6s$