A ball is thrown vertically upwards from the ground and a student gazing out of the window sees it moving upward past him at 10 ms−1 . The window is at 15 m above the ground level. The velocity of ball 3 s after it was projected from the ground is [Take g=10 ms−2 ]
a. 10 m/s , up
b. 20 ms−1 , up
c. 20 ms−1 , down
d. 10 ms−1 , down