posted by martin .
Two 20kg weights are hung from light strings that pass over frictionless pulleys. The ends of the strings are connected to a small, light spring balance, S,
calibrated in kg. The pulley axes are mounted on the wall of a lift in a 50-storey
What is the reading on the spring balance when the lift is at rest?
Make a qualitative sketch of the variation with time of the reading on S as the lift
makes a round trip, delivering passengers from the ground floor to the top floor and
then returning to the ground floor.