# AP Physics 1: 1.1 Waves

AP Physics 1: 1.1 Waves. What is the frequency of this wave motion?

AP Physics 1 | Waves |

Language | English Language |

### Transcript

two seconds One two like that What is the frequency

of this wave motion frequency and hear The dental answers

aren't all in hurts All right here we go Well

lot of the time in physics we use springs to

represent waves Why Because everybody loves this slinky that's Why

And also because springs and waves share some important features

If we think of a vertical spring going up and

down it has an amplitude like a wave does It

also has a frequency and a period So a spring

is a good stand in for the features of a

wave in this question were given the period of the

spring will the period of a wave is thie amount

of time it takes to complete one cycle In this

instance we can think of the spring hitting that ground

as the starting point of the period Right there it

springs up to its maximum height then comes back down

to the ground again Well that's one cycle one period

right there The frequency of a wave is the number

of cycle's completed by a wave per unit of time

Well looking at these two functions we can see they're

related In fact they're reciprocal Meaning If you multiply them

well they equal one Okay well so our head doesn't

end up on a spring let's focus and look at

some numbers to make its all clear If a spring

has a period of one second meaning it complete one

cycle in one second then it also has a frequency

of one second But let's speed our spring up And

if a spring has a period of point two five

seconds that it has a frequency of four cycles per

second Right All right Well if we're only given the

frequency or the period we can figure out the rest

Reciprocal with a little algebra Anyway in this question we

know the period equals two seconds We also know that

the period times the frequency equals one So the frequency

has to equal one over two seconds Which means the

frequency equals point Five seconds four point five parts So

the correct answer is a as long as we remember

The reciprocal relationship between period and frequency will be able

to knock these questions out And as long as we

keep our hands slightly cup and just rotated on the

wrist like that we can knock this beauty pageant out 00:02:35.408 --> [endTime] too