Randomized Problem

course PHY 231

If the velocity of the object changes from 4 cm / sec to 16 cm / sec in 8 seconds, then at what average rate is the velocity changing?Change rate in velocity = (16 cm/sec - 4cm/sec)/ 8 seconds

= 12 cm/sec / 8 seconds
change in rate in velocity = 1.5 cm/sec squared
A ball rolling from rest down a constant incline requires 8.2 seconds to roll the 97 centimeter length of the incline.
* What is its average velocity?
Average velocity = distance / time
v = 97 cm / 8.2 sec
v = 11.8 cm/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?
Final velocity = 2 avg velocity

This question is a continuation of the preceding. What is the average velocity of the ball in this example?

* What average rate is the velocity of the ball therefore changing?

Acceleration of ball = dv/dt

This question is a continuation of the preceding. What is the average acceleration of the ball in this example?

An automobile accelerates uniformly down a constant incline, starting from rest. It requires 10 seconds to cover a distance of 132 meters. At what average rate is the velocity of the automobile therefore changing?

Acceleration = ?

v = d x t

This definition is not specific enough for use in this course, and is not correct in the any event.

v = 133m x 10 sec

v = 1330 m/sec

133 m * 10 s = 1330 m * s, not 1330 m / s.

m * s is not generally a meaningful calculation, and is not consistent with any definition or concept relevant to this course.

Acceleration = (delta)v/(delta)t

This is a correct definition.

A = (1330m/sec - 0m/sec) / (10 sec - 0 sec)

For an object which accelerates from rest to 1330 m/s during a time interval lasting from t = 0 to t = 10 s, this would be the correct average acceleration. However is doesn't apply to the object in the current problem.

A = 1330m/sec / 10 sec

A = 133 m /sec squared

You are doing a good job of moving from definition to analysis. This is encouraging.

You do however have at least one very incorrect definition (you have at least one correct definition as well).

I'm confident you can correct this.