If a scientist wants to figure out how old a rock layer is, would it be useful to use a substance that takes a long time to break down (has a long half life), or a substance that breaks down quickly? A. A substance that breaks down slowly, because then there won't be enough left to measure

B. A substance that breaks down slowly, because then there will be enough left to measure.

C. A substance that breaks down quickly, so it will be all gone and we'll know it's old

Which of the following represents a virtual image?

As you are trying to move a heavy box of mass m, you realize that it is too heavy for you to lift by yourself. there is no one around to , so you attach an ideal pulley to the box and a massless rope to the ceiling, which you wrap around the pulley. you pull up on the rope to lift the box. use g for the magnitude of the acceleration due to gravity and neglect friction forces. once you have pulled hard enough to start the box moving upward, what is the magnitude f of the upward force you must apply to the rope to start raising the box with constant velocity? express the magnitude of the force in terms of m, the mass of the box.

More solar radiation is absorbed by earth’s surface than by