1.) A large boulder is ejected vertically upward from a volcano with an initial
ID: 2114972 • Letter: 1
Question
1.) A large boulder is ejected vertically upward from a volcano with an initial speed of 55.0 m/s. Air resistance may be neglected.
(a) At what time after being ejected is the boulder moving at 25.0 m/s?
(b) At what time is it moving 25.0 m/s downward?
(c) When is the displacement of the boulder from its initial position zero?
(d) When is the velocity of the boulder zero?
(e) What are the magnitude and direction of the acceleration while the boulder is (i) moving upward? (ii) moving downward? (iii) at the highest point?
(f) Sketch a-t, v-t, and y-t graphs for the boulder.
Explanation / Answer
a) (v = u-gt)
(25 = 55 - 9.8t)
t = 3.06s
b) (-25 = 55 - gt)
t = 8.16s
c) (s = ut - 0.5gt^2)
0 = (55t - 0.5gt^2)
t = 0 or t = 11.22s
d) (0 = 55 - gt)
t = 5.612s
e) (g = 9.8m/s^2) dowwards at all times
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