11.A train covers the first half of the distance between two stations at a speed of 40 km/h and the other half at 60 km/h. Then its average speed is:

12.A particle moves along a straight line path. After some time it comes to rest. The motion is with constant acceleration whose direction with respect to the direction of velocity is:

13.If the displacement of particle is zero, then what can we say about its distance covered?

14.A train starts from station with an acceleration 1 m/second square. A boy is 48m behind the train with a constant velocity 10 m/s, the minimum time after which the boy will catch the train is:

15.A beaker containing water is balanced on the pan of a common balance. A solid of specific gravity one and mass 5g is tied on the arm of the balance and immersed in water contained in the beaker, the scale pan with the beaker: