Question

A boy rolls down a hill on a skateboard. At time = 4 seconds, that boy has rolled 6 meters from the top of the hill. At time = 7 seconds, the boy has rolled to a distance of 30 meters. What is his average speed?

Answer 1

His average speed is 4.75 m/s

Explanation:

Here, we are interested in calculating the average speed of the boy.

At time t = 4 seconds, total distance traveled = 6 meters

The average speed here is distance/time = 6/4 = 1.5 m/s

Now at time 30 7 seconds , he has rolled 30 meters

What this actually means is that for the next 3 seconds after the initial 4 seconds, he rolled a total distance of 30-6 = 24 meters. Hence, he rolled 24 meters in the next three seconds

So mathematically, his average speed for the second part of the rolling is 24/3 = 8 meters per second

Conclusively therefore , his average speed will be (1.5 + 8)/2 = 9.5/2 = 4.75 meters per second