Thermofluids problem

[Losiracer2]

I had this unit conversions test today in Thermofluids...I messed ONE problem up, can anyone on here solve it?

The kinetic energy per unit mass is given by the formula ke=(V^2)/2. If the velocity is 20 m/sec, write the kinetic energy in units of KJ/kg.

I was so damn close but got it wrong and didn't pass the test so I have to take it again every week until I pass. First problem I nailed, third problem I blew through...just this problem I couldn't figure out. He gives us 10 min for all three. You either pass or you fail, there's no partial credit, have to get all three which SUCKS!

For kicks here's the other two

1. In one application the power output of a turbine is given by W(dot) = m(dot)delta(h). If m(dot)= 5lbm/sec and delta(h)=200 Btu/lbm, determine the turbine power in units of Horsepower. (1HP=550 ft-lbf/sec) and (778ft-lbf=1Btu)

3. The kinetic energy per unit mass is given by the formula ke=(V^2)/2. If the velocity is 20ft/sec, write the kinetic energy in units of ft-lbf/lbm

use GC=32.2 ft-lbm/lbf-sec^2

lbm is pound mass and english unit of measurement
lbf is pound force, also an english unit
as well as Btu....British Thermal Unit

[Straight Success]

Give me a minute.

[Straight Success]

First let's work the units.

What's a Joule? It's the unit of work, engergy, etc. What's work? Force through distance or the integral of pdV. In the SI system, force is in Newtons and distance is in meters.

So, we want out answer to end up in N*m/kg (kg being the mass). I didn't work it out, but if you just solve the equation and put it over 1 kg, that should be the energy or work per 1 unit of mass.

[Losiracer2]

Give me a minute.

you ONLY have 10 if you want it to count for credit haha jk

[Losiracer2]

First let's work the units.

What's a Joule? It's the unit of work, engergy, etc. What's work? Force through distance or the integral of pdV. In the SI system, force is in Newtons and distance is in meters.

So, we want out answer to end up in N*m/kg (kg being the mass). I didn't work it out, but if you just solve the equation and put it over 1 kg, that should be the energy or work per 1 unit of mass.

so 200 m^2/sec^2 gets multiplied by 1/1000 KJ/KG? so the answer is .2 KJ/KG?

[Straight Success]

The kinetic energy per unit mass is given by the formula ke=(V^2)/2. If the velocity is 20 m/sec, write the kinetic energy in units of KJ/kg.

Bold = key words.

That's right.

200 J/kg = .2 kJ/kg.

[Straight Success]

1. In one application the power output of a turbine is given by W(dot) = m(dot)delta(h). If m(dot)= 5lbm/sec and delta(h)=200 Btu/lbm, determine the turbine power in units of Horsepower. (1HP=550 ft-lbf/sec) and (778ft-lbf=1Btu)

The dots are above each variable right?

[Losiracer2]

Bold = key words.

That's right.

200 J/kg = .2 kJ/kg.

ugh, man! I had 200, was the first one done in class and then he gave me a funny look and said look it over one more time...so I did and then that confused the hell out of me b/c I thought 1m^/s^2 was 1 kJ/kg. but I fogot that kilo means 1000 and thats why I was off...all I had to do was divide by 1000. Oh well at least now I know.

The dots are above each variable right?

correct, its m^dot and W^dot right above each variable....sorry about the late response, I was wiring my old stock honda stereo in my beater DD. 13 wires each individually soldered and shrinkwrapped for the main stereo plug sucked!

[Straight Success]

ugh, man! I had 200, was the first one done in class and then he gave me a funny look and said look it over one more time...so I did and then that confused the hell out of me b/c I thought 1m^/s^2 was 1 kJ/kg. but I fogot that kilo means 1000 and thats why I was off...all I had to do was divide by 1000. Oh well at least now I know.



correct, its m^dot and W^dot right above each variable....sorry about the late response, I was wiring my old stock honda stereo in my beater DD. 13 wires each individually soldered and shrinkwrapped for the main stereo plug sucked!

You are one talented woman. Impressive actually. Not because you're a woman, but the fact that every time I read one of your post you are so damn determined and action oriented.

[Losiracer2]

You are one talented woman. Impressive actually. Not because you're a woman, but the fact that every time I read one of your post you are so damn determined and action oriented.

I'm a dude lol...there's no women in engineering...haha

[Straight Success]

I'm a dude lol...there's no women in engineering...haha

I have a bunch in a few of my classes. Some beautiful ones too. About damn time.

[Ghetto_CB7]

lower level

I had some in my lower level classes, but they are all gone now. There aren't many in ECE, but I know some in ME, Civil, and CS.

I had to take some random chem class last semester and WOW, thats a loaded degree if you are looking for a girl with a brain and some looks to boot.