Question

Assertion :When range of a projectile is maximum, its angle of projection may be ${45}^0$ or ${135}^0$. Reason: Horizontal range $R=\frac{u^2\sin 2\theta }{g}$ is same, when $\theta ={45}^0$ or ${135}^0$.

• A. Both Assertion and Reason are true and the Reason is correct explanation of the Assertion.
• B. Both Assertion and Reason are true, but Reason is not correct explanation of the Assertion.
• C. Assertion is true, but the Reason is false.
• D. Assertion is false, but the Reason is true.

Answer 1

The correct option is B Both Assertion and Reason are true, but Reason is not correct explanation of the Assertion.

Horizontal range, $s_x$ in a projectile is given as:
$s_x=\frac{u^2\sin 2\theta }{g}$ $(u\to \text{initial velocity})$
Clearly $s_x$ is maximum when $\left|\sin 2\theta \right|=1$
$\Rightarrow \theta ={45}^0$ or ${135}^0$
Hence assertion is correct and reason both are correct.