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STATEMENT-1: A body is projected from th...

STATEMENT-1: A body is projected from the ground with kinetic energy K at an angle of 60° with the horizontal. If air resistance is neglected, its K.E. When it is at the highest point of its trajectory will be K/4
because
STATEMENT-2: At the highest point of the trajectory, the direction of velocity and acceleration of the body are perpendicular to each other

A

Statement-1 is True, Statement-2 is True, Statement -2 is a correct explanation for
Statement-1.

B

Statement-1 is True, Statement-2 is True, Statement -2 is NOT a correct explanation for
Statement-1

C

Statement - 1 is True, Statement-2 is False.

D

Statement-1 is False, Statement-2 is True.

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to analyze the two statements provided regarding the motion of a projectile. ### Step-by-Step Solution: 1. **Understanding the Initial Conditions**: - A body is projected with an initial kinetic energy \( K \) at an angle of \( 60^\circ \) with the horizontal. - The initial velocity \( u \) can be related to the kinetic energy using the formula: \[ K = \frac{1}{2} m u^2 \] - From this, we can express the initial velocity as: \[ u = \sqrt{\frac{2K}{m}} \] 2. **Components of the Initial Velocity**: - The initial velocity can be broken down into horizontal and vertical components: - Horizontal component: \( u_x = u \cos(60^\circ) = u \cdot \frac{1}{2} = \frac{u}{2} \) - Vertical component: \( u_y = u \sin(60^\circ) = u \cdot \frac{\sqrt{3}}{2} \) 3. **Velocity at the Highest Point**: - At the highest point of the trajectory, the vertical component of the velocity becomes zero (\( v_y = 0 \)), and only the horizontal component remains: \[ v = u_x = \frac{u}{2} \] 4. **Kinetic Energy at the Highest Point**: - The kinetic energy at the highest point can be calculated using the remaining horizontal component of the velocity: \[ K' = \frac{1}{2} m v^2 = \frac{1}{2} m \left(\frac{u}{2}\right)^2 = \frac{1}{2} m \cdot \frac{u^2}{4} = \frac{1}{4} \cdot \frac{1}{2} m u^2 = \frac{K}{4} \] - Therefore, the kinetic energy at the highest point is indeed \( \frac{K}{4} \). 5. **Direction of Velocity and Acceleration**: - At the highest point, the direction of the velocity is horizontal (along the x-axis), while the acceleration due to gravity acts vertically downward (along the y-axis). - Since these two directions are perpendicular to each other, this confirms that statement 2 is true. ### Conclusion: - Both statements are true: - **Statement 1**: The kinetic energy at the highest point is \( \frac{K}{4} \). - **Statement 2**: The direction of velocity and acceleration are perpendicular at the highest point. - However, statement 2 does not provide the correct explanation for statement 1. ### Final Answer: - Both statements are true, but statement 2 is not the correct explanation for statement 1. Thus, the answer is (B).
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