Well if the rock doesn't move, then there is no amount of work done. There is no work done on an object if a force is applied to the object but it DOES NOT change its position, in this case is the rock.
The correct option is b i.e none is correct.
The instantaneous velocity would be zero at the top but the acceleration would not be zero at that point. This is because the acceleration is the rate of change of velocity. since, the velocity is not constant, hence the acceleration would not be zero. The correct answer would be option b: None is correct.
B.adding carpet and fabric wall covering to absorb sound
Answer:
Answer is 519.3 J
Explanation:
GPE = m x g x h
Object Height is equal to 7.2 x sin42 = 7.2 x 0.669 = 4.817m
GPE = 11 x 9.8 x 4.817 =519.3 J
Most probably m value (11kg) has been used as 7.2 mistakenly.
The ability to do work is generally know as energy.