問PHY 2000 CE MC Q.11 AND Q.12

11. The answer is C.

For 1, as the block is raising, so there is a gain in potential energy of the block. So 1 is correct.

For 2, Resulatant force acting on the object

= tension - weight

= 24 - 20

= 4 N

So, by F = ma, there is an accleration of the block.

That implies the velocity of the block increases.

By K.E. = 1/2 mv^2

The kinetic energy of the block is increasing

So 2 is correct.

For 3, By Power = work done / time

Power = Fs / t

Power = 4(4) / 2

Power = 8 W

So, this is incorrect.



12 is out of syllabus.