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Phy 231
Your 'cq_1_06.1' 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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For each situation state which of the five quantities v0, vf, `ds, `dt and a are given, and give the value of each.
• A ball accelerates uniformly from 10 cm/s to 20 cm/s while traveling 45 cm.
answer/question/discussion: ->->->->->->->->->->->-> :
v0 = 10cm/s
vf = 20cm/s
`ds = 45cm
V_avg = 30cm/s / 2 = 15cm/s
`dt = 45cm / 15cm/s = 3seconds
`dv = 10cm/s
A = 10cm/s / 3s = 3.3cm/s^2
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• A ball accelerates uniformly at 10 cm/s^2 for 3 seconds, and at the end of this interval is moving at 50 cm/s.
answer/question/discussion: ->->->->->->->->->->->-> :
vf = 50cm/s
a = 10cm/s^2
`dt = 3sec
V0 = 50cm/s - ( 10cm/s * 3sec)
V0 = 20cm/s
V_avg = (50cm/s + 20cm/s) / 2 = 35cm/s
`ds = 35cm/s * 3 sec = 105cm
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• A ball travels 30 cm along an incline, starting from rest, while accelerating at 20 cm/s^2.
answer/question/discussion: ->->->->->->->->->->->-> :
`ds = 30cm
V0 = 0
A = 20cm/s^2
Vf = sqrt(v0 + 2a`ds)
@& Be careful.
vf = sqrt(v0^2 + 2a`ds)
It doesn't make a difference on the problem you're using, since v0 = 0, but if v0 wasn't zero the units wouldn't work out, and your answer wouldn't be correct.*@
Vf = sqrt(2(20cm/s^2)*(30cm)
Vf= 34.6cm/s
V_avg = 34.6cm/s / 2 = 17.3cm/s
`dt = 30cm / 17.3cm/s = 1.73sec
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Then for each situation answer the following:
• Is it possible from this information to directly determine vAve?
answer/question/discussion: ->->->->->->->->->->->-> :
No, the final velocity must be determined first.
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• Is it possible to directly determine `dv?
answer/question/discussion: ->->->->->->->->->->->-> :
No, the final velocity must be determined first.
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10 minutes
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@& Very good. See my note.*@