A 2kg block is sliding up a surface inclined at an angle of 30° above the horizontal. The block has the speeds indicated in the figure when it passes points L and K. The distance between points L and K is 2m. Which of the following includes a correct claim about the interaction of the block and the surface with supporting evidence from the figure?

The surface is rough, because the work-energy theorem indicates the block should be traveling faster at point  K .

Explanation:

Correct. Using the work-energy theorem, the speed at point K would be U1+K1=U2+K2

0+1/2mv^21=mgh2+1/2mv^22

v2= square root v^21−2gh2

=square root (7ms)^2−(2)(10)(2m)(sin30)

v2=5.4ms.

Since the actual speed at point K is slower than this value, there must have been friction between the block and surface.

it would be c. predictability