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AP Physics 2: 1.1 Changes and Conservation Laws
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AP Physics 2: 1.1 Changes and Conservation Laws. Which of the following statements are true?

AP Physics 2: 1.5 Changes and Conservation Laws
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AP Physics 2: 1.5 Changes and Conservation Laws. Which of the following statements is correct?

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AP Physics 2: 2.5 Fields in Space. Which of the following statements is true?

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AP Physics 2: 1.1 Changes and Conservation Laws 10 Views


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AP Physics 2: 1.1 Changes and Conservation Laws. Which of the following statements are true?

Language:
English Language

Transcript

00:04

And here's your shmoop du jour brought to you by hail storms which are perfect [A hail storm on a road]

00:08

for when you want your brand new car to resemble a golf ball a vertical pipe of

00:13

uniform diameter carries water a freak hailstorm punctures two clean holes in [hail storm creates two halls in a pipe]

00:18

the pipes and streams of water began to shoot out which of the following

00:22

statements is true water spouting from the top hole has a higher velocity than

00:26

water spouting from the bottom hole or the pressure at both holes is equal and

00:32

here the potential answers... Okay so hail doesn't usually [Man with a white beard and hair in the clouds]

00:37

move horizontally but like we said this is at freak hail storm, so freaky that it

00:43

doesn't have to obey the laws of physics but that doesn't mean we get the same [Car driving down a road in a hailstorm and person whistles stop!]

00:46

luxury no we have to obey the law and right now we're dealing with officer

00:50

Bernoulli. Bernoulli's principle is an extension of the law of conservation of

00:54

energy it states that at any two points in a flowing fluid the total energy is [example of Bernoulli's principle]

00:59

the same well the equation is the pressure energy plus the potential

01:03

energy plus the kinetic energy at one point equals that at the second point

01:09

and because we're dealing with fluids instead of using M for mass, the equation

01:13

uses row for the mass per volume now in this question the pressure at each hole

01:18

is the same it's just the pressure from the atmosphere since the pipe is in [Arrows pointing to a pipe]

01:22

providing pressure at the holes, so the second statement is true well to

01:27

determine if the first statement is also true let's look at the Bernoulli [Man jumps and drags the Bernoulli principle down]

01:30

principle again yikes we're not going to lie it's a little intimidating but we

01:34

can make it a little easier on the eye on the brain first of all since the [Man staring at Bernoulli's principle with googly eyes]

01:38

pressure at both points is the same we can take out the P sub 1 and the P sub 2

01:42

now we have an equation that just deals with potential and kinetic energy or if

01:47

we think about this scenario we can set the height of the lower hole to zero and [liquid flowing out of two holes in a pipe]

01:51

state that the higher hole is at a certain height of H after all we don't

01:55

really care what happens further down the pipe we'll let whoever has to fix

01:59

this lousy piece of metal worry about that so let's say that the sub 1 part of [Man screams while repairing the pipe]

02:03

the equation is for the lower hole and the sub 2 part for the upper one well if

02:08

the potential energy of the lower hole is 0 the equation now looks like

02:12

this looking at this equation we can see that the kinetic energy at the lower

02:16

point has to be higher at the higher point some of the energy is still stored

02:20

as potential energy so the kinetic energy at the higher point has to be

02:24

lower than it is lower down the pipe and that means that the velocity at the

02:27

higher point can't be greater than at the lower point so the first statement in

02:31

the question is false and that means the correct answer is B. careful if the

02:36

weather turns ugly as if rain and wind and lightning aren't enough sometimes [Man walking in a hailstorm]

02:39

mother nature decides to throw falling objects at our heads it's like payback

02:44

for that one time we forgot to recycle a soda can [Soda can hits man's head as he crosses the road]

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