PHY 201
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The problem:
A ball starts with velocity 4 cm/sec and ends with a velocity of 10 cm/sec.
• What is your best guess about the ball's average velocity?
If I were to guess I would say that you just average the two given velocities which will give you an average velocity of 7cm/sec.
• Without further information, why is this just a guess?
It is just a guess because you would need a time or distance that it took the ball to increase to a velocity that is 6cm/sec faster.
• If it takes 3 seconds to get from the first velocity to the second, then what is your best guess about how far it traveled during that time?
Since the ball is changing velocities at a rate of 2cm/s and the initial velocity is 4cm/s then the ball would have moved 4cm the first second plus 6cm more by the second plus 8cm more by the third. 4cm + 6cm + 8cm = 18cm. The ball would have moved 18cm in three seconds.
Not bad, but your estimate is based on the velocity at the beginning of each interval. Velocity is increasing so your result is an underestimate.
• At what average rate did its velocity change with respect to clock time during this interval?
The velocity changed at an average rate of 2cm/s. This is based on the initial velocity being 4cm/s and the final velocity being 10cm/s. The time interval was 3 seconds so you get a change in velocity of 6cm/s over a time interval of three seconds which gives you an average change in velocity of 2cm/s.
`er11
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I spent approximately 10 minutes on this question.
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