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Thank you We sneak and here's your chum up duis

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You are brought to you by wave motion a topic

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of great importance to physicists and to beauty pageant contestants

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everywhere All right a spring bounces up and down such

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that the bottom of the spring hits the ground every

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two seconds One two like that What is the frequency

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of this wave motion frequency and hear The dental answers

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

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lot of the time in physics we use springs to

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

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And also because springs and waves share some important features

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If we think of a vertical spring going up and

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down it has an amplitude like a wave does It

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also has a frequency and a period So a spring

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is a good stand in for the features of a

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wave in this question were given the period of the

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spring will the period of a wave is thie amount

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of time it takes to complete one cycle In this

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instance we can think of the spring hitting that ground

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as the starting point of the period Right there it

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springs up to its maximum height then comes back down

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

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right there The frequency of a wave is the number

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

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

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

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

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

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some numbers to make its all clear If a spring

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has a period of one second meaning it complete one

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cycle in one second then it also has a frequency

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

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if a spring has a period of point two five

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seconds that it has a frequency of four cycles per

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

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frequency or the period we can figure out the rest

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Reciprocal with a little algebra Anyway in this question we

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know the period equals two seconds We also know that

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the period times the frequency equals one So the frequency

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has to equal one over two seconds Which means the

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frequency equals point Five seconds four point five parts So

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the correct answer is a as long as we remember

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The reciprocal relationship between period and frequency will be able

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to knock these questions out And as long as we

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keep our hands slightly cup and just rotated on the

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

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