physics questions 3?
A foul ball is hit straight up into the air with a speed of about 31 m/s.
(a) How high does it go?
(b) How long is it in the air?
A helicopter is ascending vertically with a speed of 8.00 m/s. At a height of 135 m above the Earth, a package is dropped from a window. How much time does it take for the package to reach the ground?
stone is thrown vertically upward with a speed of 14.5 m/s from the edge of a cliff 62.0 m high (Fig. 2-32).
(a) How much later does it reach the bottom of the cliff?
(b) What is its speed just before hitting?
(c) What total distance did it travel?
A 90 m long train begins uniform acceleration from rest. The front of the train has a speed of 21 m/s when it passes a railway worker who is standing 172 m from where the front of the train started. What will be the speed of the last car as it passes the worker? (See Fig. 2-36.)
- catarthurLv 61 decade agoFavorite Answer
use d = 1/2 a t^2 + vt
and v = at + v0
Here v0 = 31m/s and a = -9.8m/s^2, the ball will be highest when it reaches the apex where v = 0 so
0 = -9.8 t + 31
t = 31/9.8 = 3.16 s
At this time it will have reached a distance of
d = 1/2 (-9.8) (3.16)^2 + (3.16)(31) = 44.06 m
It will be in the air for 3.16s*2 = 6.32s
again d = 1/2 a t^2 + vt
-135 = 1/2 (-9.8) t^2 + 8 (t)
0 = -4.9 t^2 + 8t + 135
solve for t
t = 6.13 s
Use the same formulas for the other two questions and you should be ok.