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~ Throwing a ball: Motion in one direction ~
The boy throws the ball vertically from the top of the building. The ball travels upward for 4 seconds. a) What was the original velocity of the ball when it was thrown? b) How high above the building does the ball go? When the ball begins its descent, it passes its original position at the top of the building. c) What is the velocity of the ball at this point? d) If the building is 40m, compute the elapsed time of flight from when the ball left the boy's hand. e) At what velocity does the ball hit the ground? f) What is the acceleration of the ball at the peak of its flight? g) What is the acceleration of the ball just before it hits the ground?
v = v-original + at
Delta(x) = V-original(time) + (1/2)at^2
Ymax = V-original(time) + 1/2 at^2
a) Used velocity equation instead.
0 = Vo + (-9.8)(4)
0 = Vo + (-39.2)
39.2m/s = Vo
b) This calculation makes no sense to me. EDIT: Maybe this is better. I still don't see how a boy could possibly throw a ball twice the height of a building he's standing on top of.
Ymax = Vo(time) + (1/2) at^2
Ymax = 39.2(4) + (1/2)(-9.8)(16)
Ymax = 156-78.4
Ymax = 78.4
c)
v = Vo + at
v = 39.2 + (-9.8)(8)
v = -39.2 m/s
d)
-40 = 39.2t + (1/2)(-9.8)(t)^2
-40 = 39.2t + (-4.9)(t)^2
-4.9t^2 + 39.2t + 40 = 0
4.9t^2 - 39.2t - 40 = 0
= 39.2 plus/minus sqrt (1536.64 + 784)/9.8
= 39.2 plus/minus sqrt (2320.64)/9.8
= 39.2 plus/minus 48.17/9.8
t = 8.92 seconds
WHEW.
e) v = Vo + at
v = 39.2 + (-9.8)(8.92)
v = 39.2 + (-87.42)
v = -48.22
v = 48.22 m/s
f) -9.8 m/s^2
g) -9.8 m/s^2
Homework Statement
The boy throws the ball vertically from the top of the building. The ball travels upward for 4 seconds. a) What was the original velocity of the ball when it was thrown? b) How high above the building does the ball go? When the ball begins its descent, it passes its original position at the top of the building. c) What is the velocity of the ball at this point? d) If the building is 40m, compute the elapsed time of flight from when the ball left the boy's hand. e) At what velocity does the ball hit the ground? f) What is the acceleration of the ball at the peak of its flight? g) What is the acceleration of the ball just before it hits the ground?
Homework Equations
v = v-original + at
Delta(x) = V-original(time) + (1/2)at^2
Ymax = V-original(time) + 1/2 at^2
The Attempt at a Solution
a) Used velocity equation instead.
0 = Vo + (-9.8)(4)
0 = Vo + (-39.2)
39.2m/s = Vo
b) This calculation makes no sense to me. EDIT: Maybe this is better. I still don't see how a boy could possibly throw a ball twice the height of a building he's standing on top of.
Ymax = Vo(time) + (1/2) at^2
Ymax = 39.2(4) + (1/2)(-9.8)(16)
Ymax = 156-78.4
Ymax = 78.4
c)
v = Vo + at
v = 39.2 + (-9.8)(8)
v = -39.2 m/s
d)
-40 = 39.2t + (1/2)(-9.8)(t)^2
-40 = 39.2t + (-4.9)(t)^2
-4.9t^2 + 39.2t + 40 = 0
4.9t^2 - 39.2t - 40 = 0
= 39.2 plus/minus sqrt (1536.64 + 784)/9.8
= 39.2 plus/minus sqrt (2320.64)/9.8
= 39.2 plus/minus 48.17/9.8
t = 8.92 seconds
WHEW.
e) v = Vo + at
v = 39.2 + (-9.8)(8.92)
v = 39.2 + (-87.42)
v = -48.22
v = 48.22 m/s
f) -9.8 m/s^2
g) -9.8 m/s^2
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