phy 201
Your 'cq_1_8.1' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
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A ball is tossed upward with an initial velocity of 25 meters / second. Assume that the acceleration of gravity is 10 m/s^2 downward.
What will be the velocity of the ball after one second?
answer/question/discussion: Given v0=25m/s , a = -10m/s/s
Vf = v0 + at
Vf = 25m/s + -10m/s/s/(1 )
Vf = 15m/s
What will be its velocity at the end of two seconds?
answer/question/discussion:
Vf = 25m/s + -10m/s/s(2)
Vf = 25m/s - 20m/s/s
Vf = 5m/s
During the first two seconds, what therefore is its average velocity?
answer/question/discussion:
Vave= vf + vo /2
5 + 15 /2 = 10m/s
How far does it therefore rise in the first two seconds?
answer/question/discussion:
Vave = change in x /t
Change in x = vAve * t
Change in x = 10*2 = 20m/s
Change in x = vAve * `dt
Change in x = 10 m/s * 2s = 20m, not 20 m/s.
Use units throughout your calculations.
Note that your vAve isn't quite correct; you would average 25 m/s with 5 m/s to get vAve = 15 m/s. However your reasoning throughout is correct; the only error is in a couple of your details.
What will be its velocity at the end of a additional second, and at the end of one more additional second?
answer/question/discussion: vf = 25m/s + -20m/s/s *3
Vf = -35 m/s
Good, but acceleration is -10 m/s^2, not -20 m/s^2
At what instant does the ball reach its maximum height, and how high has it risen by that instant?
answer/question/discussion:When v0 = 0 because that is when the ball has stopped moving and has reached its max point.
Vf = v0 + at
Vf - v0 / a = t
T = 0 - 25m/s / -10m/s/s
T = 2.5s
Y = vf^2- v0/2a
Y = 0 - 25m/s / 2 * -10m/s/s
Y = 1.25m
What is its average velocity for the first four seconds, and how high is it at the end of the fourth second?
v Ave = change in x /t
vAve = 1.25 / 2.5s = .5 m/s
Vf = v0 + at
Vf = 25m/s + -10m/s/s (4)
Vf = -15m/s
(x-x0)= Vf^2 - v0^2 /2a
X = -15^2 - v0^2 / 2a
X = 225 - 625 / 2 (-10)
X = 20
Answer/question/discussion:
How high will it be at the end of the sixth second?
answer/question/discussion:
Vf = - 35m/s
X-x0 = vf^2 - v0^2 /2a
X = -30
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30min
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You are doing well here. Your reasoning is sound; you do need to orrect a few of the details.
&#At least part of your solution does not agree with the solution and comments given at the link below. You should view the solution at that link and self-critique as indicated there.
Solution
This link also expands on these topics and alerts you to many of the common errors made by students in the first part of this course. &#