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Phy 121
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.
** CQ_1_06.1_labelMessages **
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: ->->->->->->->->->->->-> :
Given:
v0 = 10 cm/s
vf = 20 cm/s
'ds = 45
Need: 'dt, a
vAve=(10cm/s+20/cm/s)/2)
=15 cm/s
'dt='ds/vAve
'dt=45 cm/ 15cm/s
=3 sec
a=(20cm/s-10cm/s)/3s
acceleration=3.3 cm/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: ->->->->->->->->->->->-> :
Given:
vf=50 cm/s
acceleration=10 cm/s^2
'dt = 3 s
v0=50 cm/s-(10cm/s^2*3s)
v0=20 cm/s
vAve=(50cm/s+20cm/s)/2
vAve=35cm/s
`ds=35cm/s*3s=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: ->->->->->->->->->->->-> :
Given:
'ds = 30 cm
v0 = 0 cm/s
a = 20 cm/s^2
vf=sqrt(v0^2+2a`ds)
=sqrt(0^2+2(20cm/s^2)(30cm))
=sqrt(1200cm^2/s^2)=34.6cm/s
vAve=(v0+vf)/2
vAve=(0cm/s+34.6cm/s)/2
vAve=17.3cm/s
'dt='ds/vAve
`dt=30cm/17.3cm/s
'dt=1.73s
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Then for each situation answer the following:
• Is it possible from this information to directly determine vAve?
answer/question/discussion: ->->->->->->->->->->->-> :
yes the problem above shows it!
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• Is it possible to directly determine `dv?
answer/question/discussion: ->->->->->->->->->->->-> :
Yes, subtract v_0 from v_f
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25 minutes
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&#Very good responses. Let me know if you have questions. &#