What is the mechanical advantage if the wheel and axle is 2 n and the output force is 20 n

In a heat engine if 1000 j of heat enters the system the piston does 500 j of work, what is the final internal energy of the system if the initial energy was 2000 j ?

Erosion of the beach is normally a slow process. however, in certain situations, large chunks of shore may wash out to sea. what could cause this to happen?

For waves in the ocean, the medium of the waves is a. air b. water c. energy d. a passing boat