Good morning today we are going to talk about kinetic energy Bo. Could you telling me what the word Kinetic symbolizes? Flipping Physics Kinetic is like having to do with motion right Like kinetic. Friction, Correct, kinetic energy is the energy associated with the motion of an object. The equation for kinetic energy is KE. 1 2 mv. Where m is the mass of the object and v is the velocity of the objective Billy? Could you satisfy specify the human rights unit for kinetic energy? Kinetic energy is in joules just like work, Mr P. That may be correct, nonetheless, I asked you to determine the units 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 era. Rhythms, squared divided by seconds squared, which is the same thing as kilograms seasons meters per second squared hours, rhythms, Right and newtons – are kilograms goes. Meters per second squared, so kinetic energy is in newtons seasons rhythms, which is joules Thanks Bobby. You are welcome. So yes, kinetic energy is in joules, Bobby can kinetic, energy ever be, negative Well, mass cannot be negative but. Velocity is likely to be, negative, Oh but. Velocity is squared in kinetic energy and the square of a negative number is always, positive so kinetic, energy can never be. Negative Also kinetic energy, just like work is a scalar. Let’s do a short example problem. Let’s say I’m razz my bike at 25 km / hour. How fast would I need to drive my Prius in order to have the same amount of kinetic energy Bo? Please solve this problem. Don’t. We need to know the masses of the objects. Mr P, Yeah. Ok, The mass of the bicycle 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 moved of the bike is 25 miles per hour and we know we are trying to solve for the race of the Prius Don’t. We need the velocity of the bicycle because it’s velocity , not accelerated in the kinetic energy equation. Not actually be borne in mind that velocity is squared, so we really merely need the magnitude of the velocity and instantaneous accelerate is the magnitude of the instantaneous, velocity, Uh sure Bobby? Please keep going Well, we know the two kinetic forces need to be equal, so the kinetic energy of the bike equals the kinetic energy of the Prius. So one half mass eras velocity squared equals one half mass durations, velocity squared. Oh everybody created mass to the party. Everybody produced mass That’s , absolutely no truth to the rumors It’s , not the same. Mass Mass doesn’t cancel out it’s, one half seasons the mass of the bike times. The velocity of the bike squared equals one half days the mass of the Prius period. The velocity of the Prius squared Subscripts, we ever is important to remember subscripts. Everybody brought one half to the party That’s , not as entertaining Bobby Nope Bo No Billy, please finish Divide both sides by the mass of the Prius and then take the square seed of the whole equation. To get to the velocity of the Prius equals the velocity of the bicycle day the square root of the quantity. The mass of the motorcycle divided by the mass of the Prius Substituting in prices, leaves us 25 miles per hour times. The square root of 86 kilograms, divided by 1 400 kilograms. We forgot to convert from miles per hour to meters 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 responses have two important toes. Yes, nonetheless, the Prius’speedometer does not display tenths of a mile per hour. Ok, that constructs ability, Mr P, And this is what the bicycle and the Prius look like when they are moving with the same amount of kinetic energy Jimmy Two Dollars. Thank you very much for learning with me today. I enjoyed learning with you . .
