An elevator is stopped at the ground floor. It starts moving upwards at constant acceleration a0 for 5 seconds. It then keeps a constant speed for 35 seconds. Finally, it slows down with an acceleration of the same magnitude (but opposite direction) −a , until it comes to a halt at the top floor. The top floor is 320 meters above the ground floor.

Question

An elevator is stopped at the ground floor. It starts moving upwards at constant acceleration a>0 for 5 seconds. It then keeps a constant speed for 35 seconds. Finally, it slows down with an acceleration of the same magnitude (but opposite direction) −a , until it comes to a halt at the top floor. The top floor is 320 meters above the ground floor.
(a) What is the maximal speed v of the elevator ? (in m/s)
(b) What is the acceleration a ? (in m/s2)

KUNOI · Answer

divide the distance 320 by time 40seconds to get speed. for acceleration, divide this speed by 5.