List of top Physics Questions on Instantaneous velocity and speed

A ball is dropped from a height of 90 m on a floor. At each collision with the floor, the ball loses one tenth of its speed. Plot the speed-time graph of its motion between t = 0 to 12 s.

A man walks on a straight road from his home to a market 2.5 \(\text {km}\) away with a speed of 5 \(\text {km}\) \(\text h^{-1}\). Finding the market closed, he instantly turns and walks back home with a speed of 7.5 \(\text {km}\) \(\text h^{-1}\) What is the 

1. magnitude of average velocity, and 
2. average speed of the man over the interval of time (i) 0 to 30 min, (ii) 0 to 50 min, (iii) 0 to 40 min ? [Note: You will appreciate from this exercise why it is better to define average speed as total path length divided by time, and not as magnitude of average velocity. You would not like to tell the tired man on his return home that his average speed was zero !].

Figure 2.14 gives the x-t plot of a particle in one-dimensional motion. Three different equal intervals of time are shown. In which interval is the average speed greatest, and in which is it the least ? Give the sign of average velocity for each interval.