Skilled burglars have broken into a prosperous Swiss bank with the intent of ste

Question

Skilled burglars have broken into a prosperous Swiss bank with the
intent of stealing a safe filled with gold. The entire safe, i.e. safe
and gold, weighs one metric ton. The burglars managed to find the
safe and they brought it to a large floor-to-ceiling window. Their
plan is to lower the safe 10.0 m onto a flat-bed truck. To this end:
they stack up 1990 kg of office furniture; tie a rope between the
safe and the furniture; place the rope over a pulley; and lower the
safe out the window

We are to assume that the furniture moves with a
constant velocity and µ^k= 0.95 between the furniture and the floor.


Will the burglars be apprehended by the police who are located 20 seconds away if at the moment they begin to lower the safe the police are notified?

Explanation / Answer

The net force is the force pulling the safe down, mg, minus the friction force supplied by the furniture, mgk, so F = msg - mfgk, and acceleration is (msg - mfgk)/(ms + mf), and since mfk>ms, the safe would not fall at all, so they would certainly be apprehended.

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