Please help me at physics..?

Question

a ball is thrown upward from a bridge with an initial velocity of 144ft/s. if the bridge is 150ft above the river flowing under it, find a.) the height to which the ball rises, b.) The time to reach the highest point, and c.) the total time to reach the water and the velocity with it hits the water.

Answer 1

(a)

Let h be the height above the bridge.

Using g = 32 ft/s^2:

0 = 144^2 - 2 * 32h

h = 324 ft. above the bridge.

(b)

If t1 is the time to maximum height:

0 = 144 - 32 t1

t1 = 4.5 sec.

(c)

The total descent from the highest point is:

324 + 150

= 474 ft.

If t2 is the additional time for the descent:

474 = 32 t2^2 / 2

t2 = 5.44 sec.

The total time to reach the water is:

t1 + t2

= 9.94 sec.

If v is the velocity on hitting the water:

v^2 = 2 * 32 * 474

v = 174 ft/sec.