Two identical stones, a and b, are thrown from a cliff from the same height and with the same initial speed. stone a is thrown vertically upward, and stone b is thrown vertically downward. which of the following statements best explains which stone has a larger speed just before it hits the ground, assuming no effects of air friction?

a. both stones have the same speed; they have the same change in ugand the same ki
b. a, because it travels a longer path.
c. a, because it takes a longer time interval.
d. a, because it travels a longer path and takes a longer time interval.
e. b, because no work is done against gravity.

b. A, because it travels a longer path.

Explanation:

If the stone A is thrown is thrown vertically upwards and another stone is dropped down directly from the same height above the ground then the stone A will hit the ground with a higher speed because it falls down from a greater height above the earth surface.

This can be justified by the equation of motion given below:

where:

final velocity

initial velocity

acceleration = g (here)

displacement of the body

Now we know that at the maximum height the speed of the object will be zero for a moment. So for both the stones A and B the initial  velocity is zero, stone B is also dropped from a height with initial velocity zero.Acceleration due to gravity is same for the stones so the only deciding factor that remains is s, displacement of the stones. Since stone A is thrown upwards it will attain a greater height before falling down.

Full change in the electric plus system

That would be kinetic energy