A person walks up a stalled escalator in 90 second. When standing on the same escalator, now moving he is carried up in 60 second. How much time would it take him to walk up the moving escalator?


Correct option is

36 s


Let the length of escalator be L. If v is the velocity if man (relative

to escalator) and of escalator, then according to given problem


Now if the person walks up on the moving escalator his velocity

relative to the ground will be (V + v). So time taken by him to

move a distance L relative to the ground will be,


which in the light of Eqns. (1) and (2) gives


i.e., the person will take 36 s to walk up to the moving escalator.



Two cars are moving in the same direction with the same speed 30 km/hr.They are separated by a distance of 5 km. What is the speed of a car moving in the opposite direction if it meets these two cars at an interval of 4 minute?


A passenger is standing ‘d’  away from a bus. The bus being to move with constant acceleration a. To catch the bus, the passenger runs at a constant speed v towards the bus. What must be the minimum speed of the passenger so that he may catch the bus?