#$&*
phy 121
Your 'cq_1_05.1' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
** **
The problem:
A ball accelerates at 8 cm/s^2 for 3 seconds, starting with velocity 12 cm/s.
What will be its velocity after the 3 seconds has elapsed?
answer/question/discussion: ->->->->->->->->->->->-> :
vf = v0 + a `dt
= 12cm/s + 8 cm/s^2 (3s)
= 12 cm/s + 24 cm/s
= 36 cm/s
#$&*
Assuming that acceleration is constant, what will be its average velocity during this interval?
answer/question/discussion: ->->->->->->->->->->->-> :
vAve = (vf + v0) / 2
= (36cm/s + 12 cm/s) / 2
= 48 cm/s / 2
= 24 cm/s
#$&*
How far will it travel during this interval?
answer/question/discussion: ->->->->->->->->->->->-> :
`ds = (vf +v0)/2 * `dt
= (36 cm/s + 12 cm/s)/2 * 3s
= 48 cm/s / 2 * 3s
= 24 cm/s * 3s
= 8 cm
24 * 3 = 72, not 8.
Just thinking about the situation, observe that:
The ball moves an average of 24 cm every second, so in 3 seconds it moves 72 cm.
Its velocity changes by 24 cm/s in 3 sec, so every second its velocity changes by 8 cm/s, giving it average acceleration of 8 cm/s^2.
#$&*
** **
30 min
** **
&#Good responses. See my notes and let me know if you have questions. &#