Question

akka initially at rest attains a speed of 20 metre per second in 5 second and move with the same speed for the next 20 seconds and then come to rest for the next 10 second plot speed time graph find acceleration, find retardation, total distance covered, average speed.​

Answer 1

Answer:

a.

b. Acceleration = change in velocity/ time

So, for the first 5 sec, a = (20-0)/5 = 4 m/s^2

For the next 20 sec, a = (20-20)/20 = 0

For the next 10 sec, a = (0-20)/10 = -2 m/s^2

c. Average speed = total distance travelled/total time.

Using third law of motion : v^2-u^2 = 2as to compute distance travelled

In the first 5 sec, 20^2 - 0^2 = 2*4*s i.e. s = 50m

In the next 20 sec, s = v*t = 20*20 = 400m

In the next 10 sec, 0^2 - 20^2 = 2*(-2)*s i..e s = 100 m

hence total distance travelled = 550m

Total time taken = 35sec

Average speed = 550/35 m/s = 15.71 m/s