Energy, work, and power?

Question

I have a test tommorow over energy, work, and power, and was wondering if you could tell me if what have below is correct and maybe give me any more tips or information??

Energy- ability to do work
Work- must make something move to do work
W=Fd
Measured in Joules
Kinectic Energy- energy of motion
KE=.5mv^2
Measured in Joules
Potential Energy- Energy of position
PE=mgh
Measured in Joules
Power- rate at which work is done
P=W/t
measured in watts

Law of conservation of energy- energy can't be created nor destroyed in closed isolated system
Work-energy Theorem- work applied to object will equal change in energy of object (Still a little confused on this)

What happens to energies in closed isolated sstem?

Be able to calculate work done when force applied isn't exactly in direction of motion (Confused)

also is a kilowatt a watt with kilo (as in times by 1000?)

Thanks so Much

Answer 1

Everything you have stated is true.

>>work applied to object will equal change in energy of object (Still a little confused on this)
Example: A book is on a shelf. It has potential energy with respect to the floor. If you do work on it and raise it to a higher shelf, it then has more potential energy. The increase is the amount of work you did.

>>What happens to energies in closed isolated sstem?
Not sure what you mean here. Energy is conserved. It could be that energy is converted from potential to kinetic, or heat.

>>Be able to calculate work done when force applied isn't exactly in direction of motion (Confused)
Example: You have an empty swimming pool. The bottom of the pool is 1 meter below a walkway across the pool. A box is on the bottom of the pool and you are trying to slide the box along the bottom below the walkway. You're pushing down on the box with a pole. If the pole is at an angle of 5 degrees with the verical, you're not very efficient in turning your effort into motion of the box - you're mostly just pushing the box against the bottom of the pool. If you get a longer pole so you can push with the pole at an angle of 70 degrees with the vertical, much more of your effort goes to moving the box. The formula is
W = F*d*cos(the angle between the force vector and the displacement vector). Essentially what you are doing is calculating the component of the force that is in the direction of the motion, and multiplying that component by the motion's distance.

>>also is a kilowatt a watt with kilo (as in times by 1000?)
Yes, 1 kWatt is 1000 Watts.

Good luck tomorrow

Answer 2

The average person can only generate something like a sustained 1/10th of a horsepower when riding a bicycle-like machine (even an elite professional rider like Lance Armstrong can only sustain about 1/3hp max - horses are very strong animals...). So no, it would not be possible to propel a public vehicle like a bus by having all passengers riding a bicycle-like generators. There's so much energy contained in Diesel fuel, Gasoline etc., and released and harnessed by engines and transmissions that it is astounding when you put it into perspective - say you had 50 people weighing an average of 170lbs on the bus and they all rode a bike/generator to their max ability. The peddling passengers would be producing just 5hp combined to pull their combined weight of 8500lbs PLUS they'd have to pull the over 30,000lbs that the bus itself weighs on top of their combined body weights!

Answer 3

learn the formalas byheart, and learn definations, and read the text book.