# Recent content by Reefy

1. ### Modes of Vibration of 3-DOF Spring Mass System

Something seems off about that because if I say A = 1, then $$A(1-ω^2) - B = 0$$ $$→$$ $$B=(1-ω^2)$$ And $$C(1-ω^2) - B = 0$$ $$→$$ $$C = B/(1-ω^2) = (1-ω^2)/(1-ω^2) = 1$$ But I still have the equation for $$B(2-ω^2) - A - C = B(2-ω^2) - 2 = 0$$ $$→$$ $$B=2/(2-ω^2)$$ which will give me...
2. ### Modes of Vibration of 3-DOF Spring Mass System

Ok, if I do that then I get A = C = 1, and then B will equal 1, 0, and -2 for the three different ω
3. ### Modes of Vibration of 3-DOF Spring Mass System

Is there another method that you know of? Can I set up a ratio of the amplitudes? My equations after assuming a solution of X1,2,3 = Asinωt, Bsinωt, and Csinωt are $$A(1-ω^2) - B = 0$$ $$B(2-ω^2) - A - C = 0$$ $$C(1-ω^2) - B = 0$$
4. ### Modes of Vibration of 3-DOF Spring Mass System

1. Homework Statement 2. Homework Equations a11 = a21 = a31 = a12 = a13 a22 = a32 = a23  \begin{bmatrix} x_{1} \\ x_{2} \\ x_{3} \end{bmatrix} =ω^2m \begin{bmatrix} a_{11} & a_{12} & a_{13} \\ a_{21} & a_{22} & a_{23} \\ a_{31} & a_{32} &...
5. ### Heat Loss Through a Short Cylinder

1. Homework Statement A short metal cylinder 145 mm in diameter and 145 mm high at 1045 K is suddenly exposed (all sides exposed) to a room air temperature at 300 K with h=25 W/m².K. Assume that for the metal k=40W/m.K, den=7800 kg/m3 and Cp=c=600 J/kg.K. Estimate (a) the time required for...
6. ### Thermodynamics Gas Mixture - Dew Point Temperature

Am I supposed to use the humidity ratio to solve this? I thought the 0.1 kg/s was the mass flow rate of dry air ω = 0.622 x (Saturated Pressure)/ (Pressure mixture - Saturated Pressure)
7. ### Thermodynamics Gas Mixture - Dew Point Temperature

The saturation pressure at that temperature is 9.14 kPa using linear interpolation with the saturation tables. Ok, so the rate given was for the mixture which is the same for all components. For some reason, I was thinking each component might have a different mass flow rate. Then the part I'm...
8. ### Thermodynamics Gas Mixture - Dew Point Temperature

1. Homework Statement Only Number 1, not number 2 2. Homework Equations Dew Point Temperature T = Saturated Temperated at Vapor Pressure Partial Pressure = (mole fraction) x (Mixture Pressure) 3. The Attempt at a Solution The dew point temperature is only dependent on the pressure of...
9. ### Gas Mixture - Dew Point Temperature

1. Homework Statement Only Number 1, not number 2 2. Homework Equations Dew Point Temperature T = Saturated Temperated at Vapor Pressure Partial Pressure = (mole fraction) x (Mixture Pressure) 3. The Attempt at a Solution The dew point temperature is only dependent on the pressure of...
10. ### DC Shunt Motor

Thanks, I see the mistake I was making! It was pretty simple, I must be tired. Appreciate the help again
11. ### DC Shunt Motor

T = PM/ω = EaIa/(2πN)
12. ### DC Shunt Motor

Ooohh. Yeah, its the conceptual idea I don't get. I don't get why we have to use mechanical power instead of electrical
13. ### DC Shunt Motor

That's what I'm unsure of. I know that Pinput - Poutput = the total losses (Copper, iron, friction). And Copper Loss is I2aRa + I2shRsh
14. ### DC Shunt Motor

Ia1 = IL1 - Ish = 25A - 1A = 24A Ia2 = IL2 - Ish = 50A - 1A = 49A
15. ### DC Shunt Motor

Pinput(1) = VtIL1 = (250 V)(25 A) = 6250 A at the first speed and it is Pinput(2) = VtIL2 = (250 V)(50 A) = 12500 A at the 2nd speed