Question

A train is travelling at a speed of `90 km//h`. Brakes are applied so as to produce a uniform acceleration of `- 0.5 m//s^(2)`. Find how far the train will go before it is brought to rest.

Answer 1

Here, `" "` Initial speed, `u` = 90 km `h^(-1)`
`" " = (90xx1000" m")/(60 xx 60 " s")`
`" " = 25" m " s^(-1)`
`" "` Final speed, `v=0" "`(The train stops)
`" "` Acceleration, `a= -0.5" m "s^(-2)`
And, `" "` Distance travelled, `s= ? " "` (To be calculated)
Now, `" "v^(2)=u^(2)+2as`
So, `" "(0)^(2)= (25)^(2)+ 2 xx (-0.5)xxs`
`" "0=625 -1 xx s`
`" "s= 625" m"`
Thus, the train will travel a distance of 625 metres before it is brought to rest.