Q. A steel safe with mass 2200 kg falls onto concrete. Just before hitting the concrete its speed is 40 m/s, and it smashes without rebounding and ends up being 0.06 m shorter than before. What is the approximate magnitude of the force exerted on the safe by the concrete?
Q. A 78-kg man stands on a spring scale in an elevator. Starting from rest, the elevator ascends, attaining its maximum speed of 1.2 m/s in 0.74 s. The elevator travels with this constant speed for 5.0 s, undergoes a uniform negative acceleration for 1.8 s, and then comes to rest. What does the spring scale register in each of the following time intervals?
(a) before the elevator starts to move
(b) during the first 0.74 s of the elevator's ascent
(c) while the elevator is traveling at constant speed
(d) during the elevator's negative acceleration