Question

A block of mass $2.0kg$ is pulled up on a smooth incline of angle ${30}^{\circ }$ with the horizontal. If the block moves with an acceleration of $1.0m/s^2$. find the power delivered by the pulling force at a time $4.0s$ after the motion starts. What is the average power delivered during $4.0s$ after the motion starts?

Answer 1

1.

$P=Fv$

$=F(u+at)$

$=(2+10)(0+1\times 4)$

$=12\times 4=48W$

2.

$P_{avg}=\frac{total-work-done}{total-time-taken}$

$=\frac{Fs}{4}$

$=\frac{F(ut+\frac{1}{2}a{t}^2)}{4}$

$=\frac{12(0+\frac{1}{2}\times 4\times 2^2)}{4}$

$=\frac{8\times 12}{4}$

$=\frac{96}{4}=24W$