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he 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?
Velocity= initial velocity + accereration * change in time
12cm/s + 8cm/s^2 * 3
=20cm/s (rounded answer)
Right, except that 3 should be 3 s.
However you didn't calculate your final result correctly.
12cm/s + 8cm/s^2 * 3s = 12 cm/s + 24 (cm/s^2) * s = 12 cm/s + 24 cm/s = 36 cm/s, not 20 cm/s.
???? i don't believe i worked that one out correctly
Assuming that acceleration is constant, what will be its average velocity during this interval?
Average velocity= 'ds/'dt
I belive that the average velocity would be 8cm/s
vAve = `ds / `dt. This is correct.
You don't show how this result gives you an average velocity of 8 cm/s. It appears that 8 cm/s is simply asserted as the average velocity, with no explanation. It is possible that you are mistaking 8 cm/s^2 as the average velocity; however 8 cm/s^2 is specified as the acceleration, and in cany case 8 cm/^2 does not have units of velocity.
This object starts at 12 cm/s, and the object speeds up. Thus
The initial velocity on this interval is 12 cm/s, and the final is 36 cm/s.
The average velocity will lie between the initial and final velocities.
The average velocity is not equal to 12 cm/s or to any lesser velocity, and it is not equal to 36 cm/s or to any greater velocity.
What therefore do you think is the average velocity on this interval?
Once you know the average velocity you can use vAve = `ds / `dt to find `ds.
How far will it travel during this interval?
36 cm
You don't specify how you got this result.
36 cm would be the distance traveled in 3 seconds at 12 cm/s.
36 cm/s is the final velocity.
But 36 cm is not the displacement of this object over this interval.
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30 minutes
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I felt that I should have understood this more....i'm still not exactly getting the average acceleration down..i don't exactly know how to figure the problem out with the cm/s^2 because you told me on that problem that the ball accelerated a certain amount but i didn't know how to figure out how far he was traveling????
You just about got the first part right, but left off units and miscalculated your result.
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