1) A rock is resting on a plank of wood

1) A rock is resting on a plank of wood. Roy pushes the plank and accelerates it in such a way that the rock is stationary with respect to the plank. The work done by static friction is _________. A. Parallel to the surface B. Zero C. Negative D. Positive

2. Celine and Barbara throw identical stones vertically upward. Celine throws her stone with an initial speed twice as that of Barbara's. Assuming no air resistance, what is the maximum height of Celine's stone compared with that of Barbara's stone? A. Equal B. Eight times C. Four times D. Two times

3. A hammer does the work of driving a nail into a wooden board. Compared to the moment before the hammer strikes the nail after it impacts the nail, the hammer's mechanical energy is _____________. A. The same B. Less, because the hammer has done work C. Less, because work has been done on the hammer D. Greater, because the hammer has done work