JEE Main 2022 · 27 Jul · Shift 2 · Physics Q34

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PhysicsSingle correct+4 / -1Question 34 of 90

A block 'A' takes 2 s to slide down a frictionless incline of 30° and length ' $l$ ', kept inside a lift going up with uniform velocity ' $v$ '. If the incline is changed to 45°, the time taken by the block, to slide down the incline, will be approximately :

2.66 s

0.83 s

1.68 s

0.70 s

Answer and worked solution

Official answer: C

Uniform lift velocity leaves the effective g unchanged. At 30°: $l=\frac12(5)(2^2)=10$ m.

At 45°. $t=\sqrt{\frac{2l}{g\sin45^\circ}}=\sqrt{2\sqrt2}\approx1.68$ s.

(C)

Topics:Newton's laws Motion in a straight line

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JEE Main 2022 · 27 Jul · Shift 2, Physics question 34