What must occur for work to be done on an object?

a. a force must hold the object in place.
b. force must be applied in a direction opposite to the motion of the object.
c. no net force should be applied to the object.
d. the object must move.

Acatapult is tested by roman legionnaires. they tabulate the results in a papyrus and 2000 years later the archaeological team reads (distances translated into modern units): range = 0.4 km; angle of launch = π/5 rad; landing height = launch height. what is the initial velocity of launch of the boulders if air resistance is negligible?

The most important difference between a wedge and an inclined plane is a. their size b. their shape c. how they are used d. what they are made of

In order of decreasing light-transmitting capabilities of materials, which is the correct sequence? a. transparent -> translucent -> opaque b. opaque -> transparent -> translucent c. opaque -> translucent -> transparent d. translucent -> transparent -> opaque