Answer:
The Kinetic Energy INCREASE in the following situations:
a)A block slides down a frictionless incline:
e)A merry go round rotates faster due to the push by a person.
Explanation:
The energy kinetics is proportional to the square of the velocity:
We study the cases:
a)A block slides down a frictionless incline:
The gravity made a positive work and the box get a extra velocity, then the kinetics energy INCREASE
b)A box is pulled across a rough floor at constant speed:
The magnitude of the velocity does not change, so the kinetics energy does not change as well
c)A stone at the end of a string is whirled in a horizontal circle at constant speed:
The magnitude of the velocity does not change, so the kinetics energy does not change as well
d)A projectile approaches its maximum height:
If the projectile approaches its maximum height, its velocity approaches to zero. Then the kinetics Energy DECREASE
e)A merry go round rotates faster due to the push by a person.
Thanks to the push, the magnitude of the velocity INCREASE, so the kinetics energy INCREASE as well