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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 will analyze both statements step by step. ### Step 1: Understanding Kinetic Energy at Projection The body is projected with an initial kinetic energy \( K \) at an angle of \( 60^\circ \) with the horizontal. The initial kinetic energy can be expressed as: \[ K = \frac{1}{2} m v^2 \] where \( v \) is the initial velocity of the body and \( m \) is its mass. **Hint:** Remember that kinetic energy is related to the mass and the square of the velocity. ### Step 2: Finding Horizontal and Vertical Components of Velocity The initial velocity \( v \) can be resolved into horizontal and vertical components: - Horizontal component \( v_x = v \cos(60^\circ) = v \cdot \frac{1}{2} = \frac{v}{2} \) - Vertical component \( v_y = v \sin(60^\circ) = v \cdot \frac{\sqrt{3}}{2} \) **Hint:** Use trigonometric identities to resolve the velocity into components. ### Step 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: \[ v_{x, \text{highest}} = \frac{v}{2} \] **Hint:** Remember that at the highest point, the object stops moving upward, so its vertical velocity is zero. ### Step 4: Kinetic Energy at the Highest Point The kinetic energy at the highest point \( K_h \) can be calculated using the remaining horizontal velocity: \[ K_h = \frac{1}{2} m v_{x, \text{highest}}^2 = \frac{1}{2} m \left(\frac{v}{2}\right)^2 = \frac{1}{2} m \cdot \frac{v^2}{4} = \frac{1}{4} \left(\frac{1}{2} m v^2\right) = \frac{K}{4} \] **Hint:** Substitute the expression for \( v_{x, \text{highest}} \) into the kinetic energy formula. ### Step 5: Analyzing Statement 1 Statement 1 claims that the kinetic energy at the highest point is \( \frac{K}{4} \). From our calculations, we found that this is indeed true. **Hint:** Verify the calculations to ensure that the kinetic energy at the highest point matches the assertion. ### Step 6: Analyzing Statement 2 Statement 2 states that at the highest point of the trajectory, the direction of velocity and acceleration of the body are perpendicular to each other. At this point: - The velocity is horizontal (along the x-axis). - The acceleration due to gravity acts downward (along the y-axis). Since the horizontal and vertical directions are perpendicular, this statement is also true. **Hint:** Consider the directions of velocity and acceleration vectors to determine their relationship. ### Conclusion Both statements are true: - Statement 1 is true because the kinetic energy at the highest point is \( \frac{K}{4} \). - Statement 2 is true because the velocity and acceleration are perpendicular at the highest point. However, Statement 2 does not provide a correct explanation for Statement 1, as the relationship between the two is not direct. **Final Answer:** Statement 1 is true, Statement 2 is true, but Statement 2 is not the correct explanation for Statement 1.
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Knowledge Check

  • When a projectile is at the highest point of its trajectory, the directions of its velocity and acceleration are

    A
    Parallel to each other
    B
    anti-parallel to each other
    C
    inclined to each other at an angle of 45 degree
    D
    perpendicular to each other
  • A particle is projected from the ground with a kinetic energy E at an angle of 60° with the horizontal. Its kinetic energy at the highest point of its motion will be

    A
    `E//sqrt(2)`
    B
    `E//2`
    C
    `E//4`
    D
    `E//8`
  • A particle is projected at an angle of 60^(@) to the horizontal with a kinetic energy E. The kinetic energy at the highest point is

    A
    E
    B
    E/4
    C
    E/2
    D
    Zero
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