Q16 / 100 · NTA Abhyas (JEE Main) 2020 · Physics · Gravitation

How many time faster than the present speed would the earth have to rotate about its axis so that the apparent weight of the bodies on the equator becomes zero? (The radius of the earth R=6.4×106 m)

  • A
    5 times
  • B
    9 times
  • C
    13 times
  • Correct answer
    D
    17 times

Solution

Let ω0 be the new angular velocity.

At the equator gE=g-Rω2

The weight mgE should be zero. gE=0

∴Rω02=g or ω0=gR

∴ω0=9.86.4×106=1.24×10-3rads

The present angular velocity of the earth is ω=2πT=2×3.1424×60×60

∴ ω=3.14×10-212×36=7.27×10-5

∴ω0ω=1.24×10-37.27×10-5=17

∴ω0=17ω

It should rotate faster by 17 times the present value.

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

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