Question 29: Motion in 2D & Vectors

Question

A ball of mass 100 g is projected with velocity $20 \mathrm{~m} / \mathrm{s}$ at $60^{\circ}$ with horizontal. The decrease in kinetic energy of the ball during the motion from point of projection to highest point is

Accepted Answer

$$\begin{aligned}
& \mathrm{k}_{\mathrm{i}}=\frac{1}{2} \mathrm{mv}^2 \
& \mathrm{k}_{\mathrm{f}}=\frac{1}{2} \mathrm{~m}\left(\mathrm{v} \cos 60^{\circ}ight)^2=\frac{1}{8} \mathrm{mv}^2 \
& \Delta \mathrm{k}=\mathrm{k}_{\mathrm{i}}-\mathrm{k}_{\mathrm{f}}=\frac{3}{8} \mathrm{mv}^2=\frac{3}{8} 	imes 0.1 	imes 400=15 \mathrm{~J}
\end{aligned}$$

Answer

20 J

Answer

5 J

Answer

15 J

Answer

zero

Motion in 2D & Vectors

A ball of mass 100 g is projected with velocity 20 \mathrm{~m} / \mathrm{s} at 60^{\circ} with horizontal. The decrease in kinetic energy of the ball during the motion from point of projection to highest point is

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