Question

A body covers half of its journey a speed of 40 m/s and other half with a speed of 60 m/s. What is the average speed during the whole journey?

Answer 1

Answer:

Average speed during the whole journey is 48 m/s

Explanation:

let total distance body covered is x

let x/2 distance cover in time t1 with speed of 40 m/s

and  x/2 distance cover in time t2 with speed of 60 m/s

$t_{1} =Distance/speed =\frac{0.5x}{40} \\t_{2} = \frac{0.5x}{60}$

Total time of travel is

$t_{1}+t_{2}=\frac{0.5x}{40} +\frac{0.5x}{60}\\t_{1}+t_{2}=\frac{1.5x+x}{120} \\t_{1}+t_{2}=\frac{2.5x}{120} \\t_{1}+t_{2}=\frac{x}{48}$

Average speed is = $total distance /total time$

=x/(x/48)

=48 m/s

Average speed during the whole journey is 48 m/s

Answer 2

Answer:

Average speed during the whole journey is 48 m/s

Explanation:

let total distance body covered is x

let x/2 distance cover in time t1 with speed of 40 m/s

and  x/2 distance cover in time t2 with speed of 60 m/s

Total time of travel is

Average speed is =  

=x/(x/48)

=48 m/s

Average speed during the whole journey is 48 m/s