AP Physics B 1.1 Waves and Optics
AP Physics B: Waves and Optics Drill 1, Problem 1. Which of the following is technically true for Max as he stands still at the edge of oblivion?
|AP Physics B||Newtonian Mechanics|
Waves and Optics
|AP Physics B/C||Waves and Optics|
|AP Physics C||Newtonian Mechanics|
Which of the following is technically true for Max
as he stands still at the edge of oblivion?
You know... other than the fact that he now has proof his parents love him?
And here are the potential answers...
This problem doesn't have a lot of numbers, so it's clearly a conceptual one.
Heck, there are no numbers at all. If we glance at the answers,
we'll see that they all have to do with the perceived pitch of Max's parents' cries.
Also, the problem give us information on the motion of his parents.
When we have waves and movement, our mind should immediately snap to the Doppler effect.
Named for Christian Doppler, it's the phenomenon that occurs when a source of waves is in motion.
Say, for example, that we had a speaker emitting a tone with a frequency of 100hertz.
A listener 1 meter away would hear a frequency of 100 hertz.
A listener 2 meters away would hear the same frequency.
No matter how far, the sound is still 100 hertz.
But, uh... what the heck is a hertz?
A hertz is a measurement of one cycle of sound per second.
One hertz every second the sound wave oscillates - moves up and down - one time.
If a sound has a frequency of 100 hertz, it oscillates 100 times in a second.
This rate of oscillation determines how high or low a sound is.
A higher frequency means a higher sound.
What if the speaker starts moving?
If the speaker moves away from the listeners, then the distance between each wave would increase.
This decreases the frequency and creates a lower tone.
On the other hand, if the speaker moves toward the listeners,
the waves would become closer together, and a higher tone would be heard.
So Max's father moving toward him will sound higher, and his mother will sound lower.
The only answer that fits this description is (D).
Next year's family vacation?