Question

Assertion: In javelin throw, the athlete throws the projectile at an angle of more than 45^∘.

Reason: The maximum range does not depend upon the angle of projection.

• A. Both assertion and reason are the correct answer, reason is the correct explanation for assertion.
• B. Both assertion and reason are correct. The answer reason is the incorrect explanation for the assertion.
• C. The assertion is correct and the reason is incorrect.
• D. Both assertion and reason are incorrect.

Answer 1

The correct option is D

Both assertion and reason are incorrect.

Option (D): Both assertion and reason are incorrect.

Explanation for Assertion: In javelin throw, the athlete throws the projectile at an angle of more than 45^∘.

1. The path taken by a javelin is the same as that of a projectile motion. So the formula of range in projectile motion is applicable.
   $R={\displaystyle \frac{u^2\sin 2\theta }{g}}$
2. As $$\sin \theta$$has a range of values from $0$ to $1$, hence for the range to be maximum $$\sin 2\theta$$should be $1$ .
3. Also,$$\sin 2\theta$$is directly proportional to the magnitude of range from the formula of range.
   $$\sin 2\theta =1$$
   $2\theta ={\sin }^{-1}1$
   $\Rightarrow 2\theta ={90}^{\circ }$
   $\Rightarrow \theta ={45}^{\circ }$
4. Hence the angle should be equal to $\theta ={45}^{\circ }$
5. Also, in javelin throw, in order to throw the javelin to a maximum far distance, the athlete has to throw it at an exact angle of ${45}^{°}$horizontal.

The explanation for reason: The maximum range does not depend upon the angle of projection.

1. From the above calculation, we can say that for maximum range the angle at which the javelin is thrown should be exactly $\theta ={45}^{\circ }$
2. And it clearly depends on the angle at which it is thrown with respect to the horizontal.

Hence, the correct answer is Option(D) Both assertive and reason are incorrect.