Question

An airplane travels at an average speed of 600 m/s on an outward flight and 400 m/s on the return flight over the same distance. What's is the average speed of the whole flight?

Note that the answer is not 500m/s but 480 m/s. Please explain why not?

Answer 1

let the distance travelled by the the plane during
outward flight`rarr`s

Also distance travelled during return flight`rarr`s

average speed`=` `("Total distance")/(Total time)`

Average speed{v}`rArr` `(s+s)/((s/v_1)+(s/v_2))`
`V=(2s)/(s((v_1+v_2)/(v_1v_2))`

`color(red)(V=(2v_1v_2)/(v_1+v_2)`

substituting values of `v_1 & v_2`:

`rArr(2xx600xx400)/(600+400)` `=color(green)(480(m)/(s)`