A body is thrown up in a lift with a velocity 5 m s- 1 relative to the lift and the time of flight is found to be 0.8 s . The acceleration with which the lift is moving up is (.g=10 m s- 2.)

Question

A body is thrown up in a lift with a velocity 5 m s- 1 relative to the lift and the time of flight is found to be 0.8 s . The acceleration with which the lift is moving up is (.g=10 m s- 2.) (A) 1.5 ms- 2 (B) 2 ms- 2 (C) 2.5 ms- 2 (D) 3 ms- 2

Tardigrade Admin · Accepted Answer

Acceleration of body w. r. t. lift =-(g +a) ∴ Time of flight of body, t = (2 u/g + a) ⇒ a=(2 u - g t/t)=((. 2 × 5 .) - (. 10 × 0.8 .)/0.8) = 2.5 ms- 2

Q. A body is thrown up in a lift with a velocity $5 m s^{- 1}$ relative to the lift and the time of flight is found to be $0.8 s$ . The acceleration with which the lift is moving up is $(g = 10 m s^{- 2})$

$1.5 m s^{- 2}$

$2 m s^{- 2}$

$2.5 m s^{- 2}$

$3 m s^{- 2}$

Acceleration of body w. r. t. lift $= - (g + a)$
$∴$ Time of flight of body, $t = \frac{2 u}{g + a}$
$\Rightarrow a = \frac{2 u - g t}{t} = \frac{( 2 \times 5 ) - ( 10 \times 0.8 )}{0.8} = 2.5 m s^{- 2}$

Q. A body is thrown up in a lift with a velocity 5ms−1 relative to the lift and the time of flight is found to be 0.8s . The acceleration with which the lift is moving up is (g=10ms−2)

1.5ms−2

2ms−2

2.5ms−2

3ms−2