phy201
Your 'cq_1_08.1' 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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SEED 8.1
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: ->->->->->->->->->->->-> :
v0= 25m/s
a= 10m/s^2
'dt = 1 s
Vf= V0 + a * 'dt
Vf= 25m/s + 10 m/s^2 * 1sec
Vf= 25m/s + 10m/s
Vf= 35m/s
#$&*
What will be its velocity at the end of two seconds?
answer/question/discussion: ->->->->->->->->->->->-> :
Vf= 25m/s + 10m/s^2 * 2sec
Vf= 25m/s + 20m/s
Vf= 45m/s
#$&*
During the first two seconds, what therefore is its average velocity?
answer/question/discussion: ->->->->->->->->->->->-> :
After two seconds average velocity is
v0+ vf/2
(25m/s + 45m/s) / 2
Vave = 35 m/s
#$&*
How far does it therefore rise in the first two seconds?
answer/question/discussion: ->->->->->->->->->->->-> :
how far is distance
'ds = vave * 'dt
'ds = 35m/s * 2 sec
'ds= 70 meters
#$&*
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 + 10m/s^2 * 3seconds
vf= 55m/s
Vf= 25m/s + 10m/s^2 * 4 seconds
Vf= 65m/s
#$&*
At what instant does the ball reach its maximum height, and how high has it risen by that instant?
answer/question/discussion: ->->->->->->->->->->->-> :
The maximum height has been reached after 4 seconds
It has reached a height of 65m/s
#$&*
What is its average velocity for the first four seconds, and how high is it at the end of the fourth second?
answer/question/discussion: ->->->->->->->->->->->-> :
vave = (25m/s + 65m/s)/ 2
Vave= 45m/s
#$&*
How high will it be at the end of the sixth second?
answer/question/discussion: ->->->->->->->->->->->-> :
'ds = vave * 'dt
'ds = 45m/s * 6 sec
'ds = 270 meters
#$&*
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about 20 min
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I was worried about the signs here I think the velocity is positive since it is going upward, accelerating back down with gravity so that would alos be positive. But then I was thinking that maybe velocity should be negative since it is going against the direction of gravity or does this make a difference.
You have the right concerns. Upward and downward are the only directions involved here, but being opposite they cannot both be positive. You have to choose your positive direction. You can choose either direction as positive; once you've made your choice anything in that direction is positive, anything opposite to that direction will be negative.
Most of your work was not done in terms of a selected positive direction, so you should submit a revision.
&#Please compare your solutions with the expanded discussion at the link
Solution
Self-critique your solutions, if this is necessary, according to the usual criteria. Insert any revisions, questions, etc. into a copy of this posted document. Mark any insertions with &&&& so they can be easily identified. &#