1.

A train is moving along a straight line with a constant acceleration 'a' . A boy standing in the train throws a ball forward with a speed of 10 m//s , at an angle of 60(@) to the horizontal. The boy has to move forward by 1.15 minside the train to catch the ball back at the initial height . the acceleration of the train , in m//s^(2) , is

Answer»

3 m `s^(-2)`
5 m `s^(-2)`
8 m `s^(-2)`
6 m `s^(-2)`

Solution :Here, `u=10ms^(-1),theta=60^(@)`
`:.u_(x)=ucostheta=10xxcos60^(@)=5MS^(-1)` and `u_(y)=usintheta=10xxsin60^(@)=5sqrt3ms^(-1)`
`:.t=(2u_(y))/(G)=(2xx5sqrt3)/(10)=sqrt(3)s`
and `1.15=u_(x)t-(1)/(2)at^(2),` where a is the acceleration of train
`1.15=5xxsqrt(3)-(1)/(2)xxaxx(sqrt(3))^(2)`
`(3a)/(2)=5sqrt(3)-1.15=8.65-1.15-7.5`
`a=7.5xx(2)/(3)=5ms^(-2)`


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