Q81 / 90 · JEE Main 2022 (24 Jun Shift 2) · Physics

A body is projected from the ground at an angle of 45° with the horizontal. Its velocity after 2 s is 20 m s-1. The maximum height reached by the body during its motion is _____ m. (use g=10 m s-2)

Correct answer: 20

Solution

Figure

After 2 s the velocity is 20 m s-1

⇒vx2+vy2=v2=400

⇒u2cos245°+usin45°-gt2=u22+u2-202=400

⇒u22+u22+400-402u=400

 ⇒u2=402u⇒u=402 m s-1

Now the maximum height of the projectile is given by,

H=u2sin2θ2g⇒H=160020×2×2=20 m

Hence, the correct answer is 20.

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