Question

A man walks for 1 minute at a speed of 1m/s and then runs for 1 min at a speed of 3 m/s along a straight track . What is the average speed of the man ?

Answer 1

Hint : Find the average speed using the formula $\dfrac{t_1 \times s_1 + t_2 \times s_2}{t_1+t_2}$. Then substitute the given values to find the average speed.

Complete step-by-step answer:
Given , Man walks 60 seconds at speed of 1 m/s and runs for 60 seconds at speed of 3 m/s
Now , average speed can be calculated by $\dfrac{t_1 \times s_1 + t_2 \times s_2}{t_1+t_2}$where $s_1,t_1$ and $s_2,t_2$ are the two speeds and their corresponding time .
Average speed of the man = $\dfrac{t_1 \times s_1 + t_2 \times s_2}{t_1+t_2}=\dfrac{60 \times 1 + 60 \times 3}{t_1+t_2}=\dfrac{3+1}{2}=2 m/s$
Hence , the average speed of the man is 2 m/s

Note: Speed, being a scalar quantity, is the rate at which an object covers distance. The average speed is the distance (a scalar quantity) per time ratio. Students before starting to solve the sum firstly need to understand the difference between average speed and speed to understand the first step to solve the problem.