A man walks 4km in 1hour and then returns to the starting point in 1hour. What is his average speed?
Average speed = total distance / total time. As per NCERT Chapter 3, equations v=u+at, s=ut+½at², v²=u²+2as describe uniformly accelerated motion. Applying correct signs and units gives 4 km/h as the result, so option B is correct.
Ref: NCERT Class 11 Physics > Chapter 3: Motion in a Straight Line > Topic: Distance, Displacement and Velocity-Time Relations