– Good morning, today we are going to talk about kinetic energy. Bo, could you please tell mewhat the word, “Kinetic” represents? Flipping Physics – Kinetic is like havingto do with motion, right? – Like kinetic friction. – Correct, kinetic energy is the energy associated with the gesture of an object. The equation for kineticenergy is KE= 1/2 mv. Where m is the mass of the subject matter and v is the velocity of the object. Billy, could you satisfy calculate the units for kinetic energy? – Kinetic energy is injoules, just like work. -[ Mr. P .] That may becorrect, nonetheless I asked you to determine theunits for kinetic energy. – OK, mass is in kilograms and velocity is in rhythms per second, but I don’t see how that is joules. – Well, that works out to be kilograms period meters squareddivided by seconds squared, which is the same thing as kilograms epoches meters per second squared eras rhythms. – Right and newtons are kilograms eras meters per second squared, so kinetic energy is in newtons days rhythms, which is joules. Thanks Bobby. – You are welcome. – So yes, kinetic energy is in joules.Bobby, can kineticenergy ever be negative? – Well, mass cannot be negative but velocity can be negative. Oh, but velocity issquared in kinetic energy and the square of a negativenumber is always positive, so kinetic energy can never be negative. – Also kinetic energy, justlike task, is a scalar. Let’s do a short example problem. Let’s say I’m riding mybike at 25 km / hour. How fast would I it is necessary drive my Prius in order to have the sameamount of kinetic energy? Bo, please solve this problem.- Don’t we need to knowthe masses of the objects? -[ Mr. P .] Yeah, OK. The mass of the motorcycle with me on it is 86 kilograms, and the mass of the Prius with me in it is 1,400 kilograms. – Let’s see, we know the masses, we know the hurried of thebike is 25 miles per hour and we know we are trying to solvefor the quicken of the Prius. – Don’t we need the velocity of the bike, because it’s velocity , not rushed, in the kinetic energy equation? – Not genuinely, rememberthat velocity is squared, so we really exclusively need the magnitude of the velocity and instantaneous rush is the magnitude of theinstantaneous velocity. – Uh, sure. – Bobby, delight keep going. – Well, we know the two kinetic energies need to be equal, so the kinetic energy of the motorcycle equals the kinetic energy of the Prius, so one half mass days velocity squared equals one half mass ages velocity squared … Oh, everybody drew mass to the party. Everybody returned mass – That’s not right. – It’s not the same mass. Mass doesn’t cancel out, it’s one half terms the mass of the bike occasions the velocity of the motorcycle squared equals one half goes the mass of the Prius goes the velocity of the Prius squared. – Subscripts, we alwayshave to remember subscripts. – Everybody brought one half to the party. – That’s not as entertaining. -[ Bobby] Nope.-[ Bo] No. – Billy, delight finish. – Divide both sides bythe mass of the Prius and then take the square beginning of the whole equation to get to the velocity of the Prius equals the velocity of the bike day the square root of the capacity, the mass of the bike divided by the mass of the Prius. Substituting in prices grants us 25 miles per hour times the square seed of 86 kilograms divided among 1,400 kilograms. We forgot to convert from miles per hour to rhythms per second. – Actually, we don’t need to because the kilograms cancel out and we are left with 6.1962, or 6 miles per hour.- OK, but shouldn’t our answerhave two significant toes? – Yes, however the Prius’ speedometer is not exhibition one-tenths of a mile per hour. – OK, that moves sense. -[ Mr. P .] And this is something that the bicycle and the Prius look like when they are moving with the sameamount of kinetic energy. Jimmy: Two Dollars! Thank you very much forlearning with me today. I experienced learning with you ..
