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# Predict/Calculate $A 9.50-$ g bullet has a speed of 1.30 $\mathrm{km} / \mathrm{s}$ . (a) What is its kinetic energy in joules? (b) What is the bullet's kinetic energy if its speed is halved? (c) If its speed is doubled?

## a) The bullet has a kinetic energy of 8.0275 joulesb) If the speed is halved the bullets kinetic energy will be 2.006875 joulesc) If the speed of the bullet were doubled it's kinetic energy would be 32.11 joules

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Kinetic Energy

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Danielle H.

November 17, 2020

After hitting a long fly ball that goes over the right fielder’s head and lands in the outfield, the batter decides to keep going past second base and try for third base. The 62.0-kg player begins sliding 3.40 m from the base with a speed of 4.35 m/s. I

##### Christina K.

Rutgers, The State University of New Jersey

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##### Marshall S.

University of Washington

##### Farnaz M.

Simon Fraser University

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### Video Transcript

Okay, so we have that a 9.5 gram bullet. Okay, so M equals 9.5 grams. Okay. Which is gonna be zero point zero 095 kilograms. Okay. 123 Yes. So 0.95 kilograms. Okay. That is the mass of the bullet. And its velocity V is 1.3 kilometers per 2nd 1.3 kilometers per second, which in meters per second is gonna be 1000 and 300 meters per second. Okay, so I'm just converting to s o units right off the bat, and we want to calculate the kinetic energy. Then we want to see what happens to the kinetic energy if we have the speed and and if we double it. Okay, so our first term is gonna be so this is a B. C. Eve's gonna do these one after the other. So we got 1/2 times 0.95 1/2 times 0.95 and again. One halftime. 0.0 95 Okay. Remember that kinetic energy is 1/2 m v squared. All right, and then ah, this is just gonna be with a regular speed, which is 13 100 meters per second. Okay, if we have that, that's gonna be 650 meters per second. And if we double that initial speed, Okay, it's gonna be Ah, 2600 meters per second. All right, then, if we calculate this Ah, the 1st 1 is gonna be at eight. Jules, 2nd 1 is going to be about to Jules, and the 3rd 1 is going to be about 32 jewels. Okay, so check it out. This 3rd 1 was doubled and this 1st 1 was halved. Okay? And the 3rd 1 is way bigger than the middle one. We could say right. That's because the energy scales with the square of the velocity. So the the like a doubling off velocity. Okay. Has ah lot more effect when you have ah, square. Okay.

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#### Topics

Work

Kinetic Energy

##### Christina K.

Rutgers, The State University of New Jersey

LB
##### Marshall S.

University of Washington

##### Farnaz M.

Simon Fraser University

Lectures

Join Bootcamp