Does heat engine follow the laws of conservation energy?

Which surface feature of the moon is characterized by mountainous areas? terrae craters maria regolith

What are atoms of the same element with varying number of neutrons

Alead ball is dropped into a lake from a diving board 5m above the water . it hits the water with a certain velocity and then sink with constant velocity in bottom . it reaches the bottom 5 second after it is dropped if g= 10m/s2 . find depth of the lake and average velocity of the ball ?