Question

A body travels at a speed of 10 m s${}^{-1}$ for a time interval 't' and next at a speed of 40 m s${}^{-1}$ for next time interval 't'. Find average speed for the total journey.

• A. $40m{s}^{-2}$
• B. $20m{s}^{-2}$
• C. $5m{s}^{-2}$
• D. $25m{s}^{-2}$

Answer 1

Answer: (D)

$25m{s}^{-2}$

Average speed $=\frac{totaldistance}{totaltimetaken}$

Total distance for time interval $t_1=t$ and $t_2=t$ is

$=10timest+40\times t=50tmetres$

Total time = $t_1+t_2=t+t=2tseconds$

So average speed $=\frac{50t}{2t}=25m{s}^{-1}$