A projectile is thrown at an angle theta to t | vedclass

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(B) The power delivered by a force $\vec{F}$ is given by $P = \vec{F} \cdot \vec{v}$,where $\vec{v}$ is the velocity vector.Here,the force is gravity,

Vedclass · Accepted Answer

Power delivered by gravity at $O'$ is negative

Vedclass · Answer

(B) The power delivered by a force $\vec{F}$ is given by $P = \vec{F} \cdot \vec{v}$,where $\vec{v}$ is the velocity vector.Here,the force is gravity,$\vec{F} = m\vec{g} = -mg\hat{j}$.At point $O$ (start),the velocity $\vec{v}$ has an upward vertical component. Thus,$\vec{F} \cdot \vec{v} = (-mg\hat{j}) \cdot (v_x\hat{i} + v_y\hat{j}) = -mgv_y$. Since $v_y > 0$,the power is negative. Statement $A$ is correct.At point $A$ (highest point),the velocity is purely horizontal,so $\vec{v} = v_x\hat{i}$. Thus,$P = (-mg\hat{j}) \cdot (v_x\hat{i}) = 0$. Statement $D$ is correct.At point $O'$ (end),the velocity $\vec{v}$ has a downward vertical component. Thus,$v_y  0$. The power is positive. Statement $C$ is correct.Since statement $C$ is correct,statement $B$ (which says power at $O'$ is negative) is the wrong statement.

Column $I$	Column $II$
$(A)$ Relative acceleration between two	$(p)$ $0$ $SI$ unit
$(B)$ Relative velocity between two	$(q)$ $5$ $SI$ unit
$(C)$ Horizontal distance between two	$(r)$ $10$ $SI$ unit
$(D)$ Vertical distance between two	$(s)$ $20$ $SI$ unit

$A$ projectile is thrown at an angle $\theta$ to the horizontal from $O$ and it hits the ground at $O'$. During the entire motion (select the wrong statement):

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