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course phy 201
sep. 27 5:30am
Assignment 2If the velocity of the object changes from 5 cm / sec to 14 cm / sec in 6 seconds, then at what average rate is the velocity changing?(14cm/s - 5cm/s) /6
V= 4.5cm/s/6sec =.75 cm/sec^2 = accel.
It requires 9.4 seconds, starting from rest, for a ball to roll the 57 centimeter length of a uniform incline.
• What is its average velocity? 57 cm/9.4sec =6.1cm/sec
An object which accelerates uniformly from rest will attain a final velocity which is double its average velocity.
• What therefore is the final velocity of this ball? 6.1cm/sec *2 =12.2 cm/sec
• What average rate is the velocity of the ball therefore changing? 6.1cm/sec / 9.4sec =.65cm/sec^2
At what average rate does the velocity of an airplane change, if it accelerates uniformly down a runway, starting from rest, requiring 15 seconds to cover a distance of 178 meters. 178m/15sec =11.87m/sec /15sec =.79m/s^2
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178m/15sec =11.87m/sec /15sec =.79m/s^2 implies, among other things, that
178m/15sec =.79m/s^2
The left- and right-hand sides are clearly not equal so this is a false statement.
I understand what you are doing here, but you really don't want to use the = sign for train of thought. The = sign means that two quantities are equal, and nothing else.
Having said that, there is an error in your train of thought.
11.87 m/s is the average velocity.
However you wouldn't divide this by 15 sec. to get the acceleration. You would divide the change in velocity by 15 seconds.
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