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Playlist AP® Physics 1: Changes and Conservation Laws 11 videos

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AP Physics 1: 1.1 Changes and Conservation Laws
385 Views

AP Physics 1: 1.1 Changes and Conservation Laws. What is the speed of the other piece of wood?

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AP Physics 1: 1.2 Changes and Conservation Laws
205 Views

AP Physics 1: 1.2 Changes and Conservation Laws. Why is energy lost in inelastic collisions?

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AP Physics 1: 1.3 Changes and Conservation Laws
263 Views

AP Physics 1: 1.3 Changes and Conservation Laws. How fast is the particle falling at the instant before it hits the ground?

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AP Physics 1: 1.3 Changes and Conservation Laws 263 Views


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AP Physics 1: 1.3 Changes and Conservation Laws. How fast is the particle falling at the instant before it hits the ground?

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Transcript

00:00

Thank you We sneak and here's your shmoop too sure

00:05

brought to you by falling objects The story goes that

00:08

isaac newton discovered universal gravity when an apple conked him

00:11

on the head But the real question is was it

00:13

red or was it green All right a particle slides

00:16

down a ramp and she tours on only often adds

00:18

it is twenty meters tall if it's moving it twenty

00:22

five meters a second in ways fifteen kilograms is it

00:24

shoots off the edge How fast is it falling at

00:28

the instant before it hits the ground right near the

00:31

potential answers All right well just be interesting So how

00:34

do we combine the horizontal speed of an object with

00:37

its vertical speed from gravity to find out how fast

00:40

it's falling thinking about terminal velocity here Well actually we

00:44

don't combine them at all It doesn't matter how fast

00:47

an object moves for izon aly the acceleration of gravity

00:51

is a constant downward force They'll consider this if a

00:55

bullets fired from a gun on a perfectly horizontal plane

00:58

and at the same time a bullet drops from a

01:00

hand at the same height as the gun Both bullets

01:03

Will hit the ground at the exact same instant Pretty

01:07

cool huh Yeah So let's address this question by first

01:11

looking at the potential energy of the particle Potential energy

01:15

remember equals mass times gravity times height All right well

01:21

when we plug our numbers into that equation we see

01:24

that the potential energy of this particle at the moment

01:27

it leaves the ramp is three thousand jewels So speaking

01:31

gravitationally the total mechanical energy at the moment the particle

01:34

leaves the ramp is three thousand jewels After all mechanical

01:37

energy equals potential energy plus kinetic energy And at the

01:41

very instant the particle leaves the ramp it hasn't started

01:44

falling yet So the kinetic energy is zero So what

01:48

will the kinetic energy be right before the particle hits

01:50

the ground Well at that point there will be no

01:53

more potential energy So if the total mechanical energy of

01:56

this system is three thousand jewels and the potential energy

01:59

is zero then the kinetic energy will have to be

02:02

three thousand jewels We have to remember the formula for

02:05

kinetic energy which is kinetic energy equals one half mass

02:08

times velocity squared right here saying wake unplugging our numbers

02:12

and solve for velocity Well three thousand jewels equals one

02:15

half times fifteen kilograms Times velocity squared little algebra and

02:20

we'll see that the velocity is twenty meters a second

02:23

So the correct answer is option a When dealing with

02:25

falling objects potential energy is pretty much always involved Remember

02:28

how to calculate it and remember how it relates to

02:31

connecticut and mechanical energies but leave falling objects to theoretical

02:35

problems In the real world they tend to cause issues 00:02:38.733 --> [endTime] now

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