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An automobile travelling with a speed 6...

An automobile travelling with a speed `60 km//h` , can brake to stop within a distance of `20 m` . If the car is going twice as fast i. e. , `120 km//h`, the stopping distance will be

A

`20 m`

B

`40m`

C

`60m`

D

`80 m`

Text Solution

Verified by Experts

The correct Answer is:
D
The braking retardation will remain same ans assumed to be constant, let it be a From `3rd` equaiton of motion,
`v^(2) = u^(2) +2as`
`1st` case `0 = (60 xx (5)/(10))^(2) - 2a xx s_(1)`
`rArr s_(1) = ((60 xx 5//18)^(2))/(2a)`
`2nd` case `0 = (120 xx (5)/(18))^(2) - 2a xx s_(2)`
`rArr s_(2) = ((120 xx 5//18)^(2))/(2a)`
`:. (s_(1))/(s_(2)) = (1)/(4)`
`rArr s_(2) = 4s_(1) = 4 xx 20 = 80 m`.
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