Q50 / 103 · NTA Abhyas (NEET) 2020 · Physics · Motion In One Dimension

An automobile travelling at 50 km h-1, can be stopped at a distance of 40 m by applying brakes. If the same automobile is travelling at 90 km h-1, all other conditions remaining the same and assuming no skidding, the minimum stopping distance in metre is

  • A
    72
  • B
    92.5
  • C
    102.6
  • Correct answer
    D
    129.6

Solution

According to kinematic equation,

v 2 = u 2 +2as

Therefore, the stopping distance is,

s= v 2 − u 2 2a

Therefore,

s∝ u 2 as v=0 and a=constant

⇒ s 2 s 1 = ( u 2 u 1 ) 2

Therefore, new stopping distance is,

s 2 = s 1 ( u 2 u 1 ) 2

s 2 =( 40 ) ( 90 50 ) 2

s 2 =129.6 m

Hence, the correct answer is option: 'D'.

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