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Question

Physics Question on projectile motion

A body is projected from the ground at an angle of tan1(87)\tan^{-1} \left( \frac{8}{7}\right) with the horizontal. The ratio of the maximum height attained by it to its range is

A

8 : 7

B

4 : 7

C

2 : 7

D

1 : 7

Answer

2 : 7

Explanation

Solution

For a projectile projected at angle θ\theta;
Maximum height, Hmax=u2sin2θ2gH_{\max }=\frac{u^{2} \sin ^{2} \theta}{2 g}
and range, R=u2sin2θgR=\frac{u^{2} \sin 2 \theta}{g}
\therefore Ratio =HmaxR=(u2sin2θ2g)(u2sin2θg)=tanθ4=\frac{H_{\max }}{R}=\frac{\left(\frac{u^{2} \sin ^{2} \theta}{2 g}\right)}{\left(\frac{u^{2} \sin 2 \theta}{g}\right)}=\frac{\tan \theta}{4}
Here, θ=tan187\theta=\tan ^{-1} \frac{8}{7}
tanθ=87=874=27\Rightarrow \tan \theta=\frac{8}{7}=\frac{\frac{8}{7}}{4}=\frac{2}{7}