An automobile moving at a speed of `72kmh^(-1)` reaches the foot of a smooth incline, when the engine is switched off. How much distance does the automobile go up the incline before coming to rest. The angle of inclination with horizontal is `30^(@)` and `g=9.8 ms^(-2) ?`

Explanation

Here,`u=72km//h=(72xx1000)/(60xx60)m//s=20m//s`
`theta=30^(@), g=9.8m//s^(2),s=?upsilon=0`
Retardation up the smooth incline,
`a=-gsintheta=-9.8 sin30^(@)=-4.9m//s^(2)`
From `upsilon^(2)-u^(2)=2as`
`0-20xx20=2(-4.9)s`
`s=(-400)/(-9.8)=40.8m`