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Phy 201
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A ball accelerates uniformly as it rolls 20 cm down a ramp, starting from rest, in 2 seconds.
• What are its average velocity, final velocity and acceleration?
answer/question/discussion: ->->->->->->->->->->->-> :
The average velocity of the ball is 10 cm/s. The average acceleration of the ball is 10 cm/s. The final velocity of the ball is 20 cm/s^2.
Vf = v0 + a * `dt
Vf = 0 + 10 cm/s * 2 s
Vf = 0 + 20 cm/s^2
Vf = 20 cm/s^2
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• If the time interval is in error so that it is 3% longer than the actual time interval, then what are the actual values of the final velocity and acceleration?
answer/question/discussion: ->->->->->->->->->->->-> :
2 * .03= .006, * 100 = 6
The actual value of acceleration is 3.3 cm/s. The actual value of final velocity is:
Vf = v0 + a * `dt
Vf = 0 + 3.3cm/s * 6 s
Vf = 0 + 19.8cm/s^2
Vf = 19.8cm/s^2
@& The actual time interval is about 3% shorter than the given time interval.
You have to find the actual time interval, then use it to calculate average velocity, final velocity and acceleraiton.*@
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• What is the percent error in each?
answer/question/discussion: ->->->->->->->->->->->-> :
20cm/s^2 - 19.8cm/s^2 / 19.8cm/s^2 * 100 = about 1.01%
The percent error for final velocity is about 1.01%.
10cm/s - 3.3cm/s / 3.3cm/s * 100 = about 203%.
The percent error for final velocity is 203%. (This is definitely wrong, but I’m not quite sure how else to solve for this answer, so I am giving my best guess).
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• If the percent error is the same for both velocity and acceleration, explain why this must be so.
answer/question/discussion: ->->->->->->->->->->->-> :
The percent error is not the same, but I feel that they should be because acceleration directly affects final velocity.
• If the percent errors are different explain why it must be so.
answer/question/discussion: ->->->->->->->->->->->-> :
The percent errors are different because I believe I calculated them wrong.
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*#&!*#&!
@& As you suspected you didn't calculate your quantities correctly.
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