Question

Dwayne ‘The Rock’ Johnson needs to escape from the fourth floor of a burning building (in a movie). He ties a rope around his waist and ties the other end to a 63 kg desk. Then he climbs out of a window and begins to lower himself down. The rope becomes taut when he lets go of the window sill. Then the desk begins to slide on the floor and he starts to accelerate downwards (starting from rest). Dwayne has a mass of 118 kg. The smooth window sill acts as a frictionless pulley. The desk is 10 m from the window. The kinetic friction of the desk sliding on the floor is 370 N. How fast is he travelling when the desk reaches the window? (Hint: Unbeknownst to the audience, The Rock aced Physics 1200 and knows that the tension in the rope is not 370 N).

Answer 1