Q1. There is an escalator on which a man walks when it is stationary and takes 90 sec. When the man is stationary and the escalator is moving it takes 60 sec. So how much time will the man take to cross the escalator by walking on it while the escalator is running too. My solution is Vmg = vel. Of man wrt ground = +L/90 L is the length of elevatorVme = vel.of man wrt escalator = ??Veg = vel of escalator wrt ground = +L/60As per my studies in HC Verma bookVmg = Vme + VegOr Vme = Vmg – Veg = L/90 – L/60 = -L/180 But the answer is L/36 how?? Q.2 An elevator whose floor to ceiling distance is equal to 2.7m starts ascending with a constant acceleration of 1.2 m/s/s. Two sec after it starts a bolt begins to fall from the ceiling of the elevator. I am able to calculate time of fall and displacement of bolt wrt ground frame but I am stuck at the calculation of distance covered by bolt wrt ground. Please explain comprehensively. Q3 A train is moving with a constant speed of 5m/s and there are two persons A and B standing at a separation of 10 m inside the train. Another person C is standing on the ground. A moves towards B and back to its position in 10 seconds with constant speed. I am again able to calculate the displacement of A wrt to frame of C but I am stuck at the calculation of distance covered by A wrt to frame of C. Please explain comprehensively. And hence finally show me a way to calculate distance in relative motion as displacementcan be easily calculated by me. Q.4 An airplane flies northward from town A to B and then Back again. There is a steady wind blowing towards North so that for the first stage of the trip the airplane is flying in the same direction as the wind and for the return trip the airplane is flynig directly into the wind. The total trip time Tw as compared to the the total trip time in the absence of wind To isA Tw=ToB Tw > ToC TwD Tw= 2ToThe answer is B how
Pritesh Ramya , 8 Years ago
Grade 11
