phy 121
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Asst 8 Question 1
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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: ->->->->->->->->->->->-> :
v=v0 + at
v=25m/s + (-10 m/s^2)1s
v=15m/s
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What will be its velocity at the end of two seconds?
answer/question/discussion: ->->->->->->->->->->->-> :
v=v0+at
v= 25m/s + (-10m/s^2)2sec
v= 5 m/s
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During the first two seconds, what therefore is its average velocity?
answer/question/discussion: ->->->->->->->->->->->-> :
vAve = (15m/s + 5 m/s)/2
vAve= 10 m/s
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That would be the average velocity during the 1-second interval between t = 1 sec and t = 2 sec.
The initial velocity for the first two seconds, i.e., for the interval from t = 0 sec to t = 2 sec, occurs at t = 0 sec and is 25 m/s. The final velocity for this interval occurs at t = 2 sec and is 5 m/s.
How far does it therefore rise in the first two seconds?
answer/question/discussion: ->->->->->->->->->->->-> :
If we add the 15 + 5 = 20 meters
You don't add velocities to get displacement.
The units could alert you to the error:
15 m/s + 5 m/s = 20 m/s, not 20 meters.
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What will be its velocity at the end of a additional second, and at the end of one more additional second?
answer/question/discussion: ->->->->->->->->->->->-> :
v= v0 + at
v= 25m/s + (-10m/s^2)3s
v= -5m/s
v= v0 + at
v= 25 m/s + (-10m/s^2)4s
v= -15 m/s
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At what instant does the ball reach its maximum height, and how high has it risen by that instant?
answer/question/discussion: ->->->->->->->->->->->-> :
I believe the ball reaches its max height at about 2 1/2 seconds.
I think it goes about 22 1/2 meters.
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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= (25 m/s + -15 m/s)/2=5 m/s
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How high will it be at the end of the sixth second?
answer/question/discussion: ->->->->->->->->->->->-> :
I assume it will hit the ground during this time or be caught because it has already covered the area that it has been tossed at this point.
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Much of your reasoning is correct. Some details are incorrect, but you're making good progress.
&#Please compare your solutions with the expanded discussion at the link
Solution
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