Post Module Q. 14

[William Lan 2l]

14. For large everyday objects does Heisenberg's uncertainty (indeterminacy) principle play any measurable role?

A. Yes, the uncertainties in position, speed, and momentum of a stationary object are noticeable or measurable.

B. Yes, the uncertainties in position, speed, and momentum of a moving object are noticeable or measurable.

C. No, the uncertainties in position, speed, and momentum of a stationary object are not noticeable or measurable.

D. No, the uncertainties in position, speed, and momentum of a moving object are not noticeable or measurable.

I put C, why is this wrong?

[K Stefanescu 2I]

I think the answer should be D rather than C because Heisenberg's uncertainty equation inherently requires some movement (given that p= mass* velocity of some sort) in order to solve for the position of the particle in question. If the position is given and momentum is being solved for, velocity/speed cannot be zero because to do so would give not allow for uncertainty. Therefore, the particle cannot be stationary. Thus, answers A and C can safely be eliminated, and as we know that changes to the position/speed/momentum of large objects are negligible, B can be eliminated as well, leaving D as the correct answer.

[Brigita1D]

A really good explanation of this concept is shown in the video module for the uncertainty principle. The experiment with the baseball, detector, and light source is a good representation as to why the uncertainties of large objects are not noticeable. Based on the diagram, we know the momentum of the baseball because the detectors signal when the baseball hits the light source and so we then know the distance between the two light sources. Therefore, the time that it took for the baseball to reach the second light/detector is also known. The momentum of the baseball or other large object is larger than the momentum of the photon being ejected by the light source, so that is why the the baseball does not move from the straight pathway. If a small object such as an electron comes into contact with a photon, the electron changes its direction. This is why the distance that the electron has to travel between two detectors is uncertain.
The answer is D because the mass of a large object will not cause a person to say that the position or momentum of, for example, a baseball is questionable. A photon is not able to cause the baseball to change course because the momentum of the baseball is so much bigger than the momentum of the photon.

[Wenxin Fan 1J]

The answer is D because the uncertainty principle refers to objects with momentum (m x v). Therefore, the answers involving stationary objects are not applicable.

Wenxin Fan- 1H