For work to be done on an object,
a. some force need only be exerted on the object.
b. the object must move some distance as a result of a force.
c. the object must move, whether or not a force is exerted on it.
d. the object must not move.

Stars x and y are both bluish main sequence stars. star x has a higher absolute brightness than star y. how do the two stars compare? explain

A1000-kg weather rocket is launched straight up. the rocket motor provides a constant acceleration for 16-s, then the motor stops. the rocket altitude 20-s after launch is 510-m. you can ignore any effects of air resistance. a. what was the rocket’s acceleration during the first 16-s? b. what is the rocket’s speed as it passes through a cloud 5100-m above the ground?

Diamond will scratch quartz. true or false