Physics 14

Quiz 2

This is a closed note, closed book quiz. Please try to be neat, clear and concise. The points allocated to each question are shown in parentheses following the question.

1.      a) Distinguish between velocity and acceleration. (2)

Velocity is the time rate of change of position whereas acceleration is the time rate of change of velocity. As the text mentions acceleration measures how fast how fast changes. Both quantities are vectors.

b) Cite an example of something that undergoes acceleration while moving at constant speed. Can you give an example of something that accelerates while traveling at constant velocity? Explain. (3)

An example of an object accelerating but maintaining constant speed would be a car rounding a corner at constant speed. In such case the direction of motion, and hence the velocity, changes. If the velocity is constant, by assumption it does not change, thus there can be no acceleration in such case.

2.      a) When are you most aware of motion in a moving vehicle- when it is moving steadily in a straight line or when it is accelerating? (2)

One is most aware of their motion when they are accelerating. In fact, within a smoothly moving train or car traveling at constant velocity if one were to shut their eyes they would not be able to distinguish their state from sitting at their breakfast table.

Accelerated motion is, on the contrary, quite different. While in a car or train that makes a sudden stop we are thrown forward – we feel a force pulling us forward. Such phenomena do not occur while sitting at the breakfast table. Another case of acceleration occurs when one deviates from straight- line motion – for instance while rounding a corner. In such case one feels a force pulling them outward.

b) Can an object reverse its direction of travel while maintaining a constant acceleration? If so cite an example. If not explain why. (3)

Yes, a familiar example is a ball being thrown upward. In such a case the ball has a constant acceleration downward and reverses its direction (comes momentarily to rest) at the top of its rise.