From the edge of a rooftop, you toss a green ball upward with an initial velocity of 10 m/s and a blue ball downwards with the same initial speed. air resistance is negligible. when they reach the ground below
a. the green ball will be moving faster than the blue ball.
b. the blue ball will be moving faster than the green ball.
c. the two balls will have the same speed.

c.The two balls will have the same speed.

Explanation:

When two balls green and blue both are moving with initial velocity 10m/s.

The green ball has been tossed  upward and blue ball downwards.

Air resistance is negligible means there is no force which oppose the motion of balls.

When blue balls has been tossed downward then the blue ball will move under the gravity.

When green fall downward then the ball falls under the gravity because there is no air resistance.

Therefore, both balls move with acceleration due to gravity when they wil reach at ground.

Therefore, the velocity of both balls are same.

Hence, the two balls will have the same speed.

Option c is true.