a pulley is suspended from the ceiling with a clamp. on its left hand side hangs a mass m1 = 1 kg with a length of rope 20 m. on the right hand side there is another pulley. to the left of the second pulley hangs a mass m2 of mass 2 kg and to the right side of the 2nd pulley hangs mass m3 = 3 kg. the entire system is now released from rest. find acceleration of m1, m2 and m3 and the time taken by m1 to rise up to the level of the first pulley. assumptions : standard assumptions of no friction, massless pulleys, etc. other problem : there is a weight suspended by a string from the compartment of a train which is accelerating at a value of a and the the string makes an angle arctan a/g with the ceiling normal. Now the train rushes along an uniform straight track on an inclined plane with uniform velocity and the angle is still arctan a/g. How does a passenger on the train determine whether the train is on flat land or an inclined plane ?