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All right here's your shmoop du jour brought to you by slingshots well the [Slingshots with rocks falling behind]

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most famous slingshots probably from the story of David and Goliath and if you

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are intimidated by the AP test well think of yourself as David and the AP [David holding a slingshot staring at the giant Goliath]

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test as Goliath then maybe shmoop would you know be the slingshot or would shmoop

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be the rock in the slingshot maybe your pencil would be the rock look this [a rock with the shmoop logo in Davids slingshot]

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analogy is a working process so let's just move on a rock is launched from a

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slingshot at an angle between zero and 90 degrees and lands at the same height

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from which it was launched which of the following are true about the rock select

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two answers and here the options [muttering]

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we here at shmoop would just like to remind you that slingshots should not be aimed at

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people no matter how obnoxious your little brothers being compared to a lot [Boy aiming a slingshot at his younger brother]

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of the other questions we've worked through this one's pretty vague after

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all we don't even know the mass of the rock or the tension on the slingshot and [A rock with mass written on and a slingshot]

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we're told that the angle of launch is somewhere between 0 and 90 degrees that's a

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big diff we're physicists we like specifics but it's ok we're thinking

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conceptually here a big picture and one big part of the big picture is gravity [Boy looking at Earth from outer space]

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well gravity is always acting on everything even when an object is moving

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upward gravity is still pulling it downward so option B is one of the [Boy attempting to para-sail drops down into the water]

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correct choices the acceleration of gravity is yes constant and if B is

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correct that means C is incorrect gravity doesn't care about what angle

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the rock is launched at gravity just does one thing it isn't picky option A [person bungee jumping]

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is wrong as well in a closed system energy is conserved so all along its

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flight the rock isn't losing energy the kinetic energy is only lost when the [man is struck by a rock and gives thumbs up]

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rock hits the ground and the energy is absorbed by the earth which means that

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option D is our other correct answer the rock has the same kinetic energy right

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before it hits the ground as it does when it's launched think about it this

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way the rock travels in an arc when it's launched the rock requires a certain [An arc outlining the moving rocks path]

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amount of kinetic energy to reach the peak of that arc at the highest point of

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the arc some of the kinetic energy has been converted to potential energy but [rock's kinetic energy converted to potential energy at the peak of the arc]

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for it to fall gravity has to exert force and by the time the rock is back

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to its starting elevation that potential energy is back

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to its old kinetic cell as long as the rock doesn't encounter anything as its

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[rock smashes into a flying bird] flies it will keep all its energy that's part of Newton's first law and it always

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comes back to that old guy all right so let your physics knowledge fly from the

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slingshot of your brain and conquer the scary giant that is the AP physics test [student with a slingshot on his head staring at the giant Goliath]

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there we go nailed it!

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