# Search results

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
16. ### DC Shunt Motor

I dont know why it says W. It is ohms. The load current is the current supplied by Vt.
17. ### DC Shunt Motor

1. Homework Statement A 250V shunt dc motor runs at 1000rpm while taking a current of 25 A. The motor has armature and field resistance as 0.2W and 250W respectively. Calculate (a) The speed when the load current is 50A. (b) Armature torque developed at both speeds. 2. Homework...
18. ### Power Correction Unity

Thanks, I really appreciate it.
19. ### Power Correction Unity

Zc = Vc/Ic = (240 < 0°)/(15 < 90°) = 2.67 < -90° which means Xc = -2.67i = -i/(ωC) Edit: Nvm I see that I must've mistyped in my calculator. Zc = 16 < -90° Now I got C = 199 μF
20. ### Power Correction Unity

Hmm ok so I drew the diagram on a graph and got that IC = √[IL2 - I2] which gave me IC = 15 A Using the voltage source, which is in parallel with the capacitor, I found reactance Xc which gave me C = 1.19mF. Did I make a mistake somewhere?
21. ### Power Correction Unity

Ok, so when the problem says that it has a power factor of 1.0, they are talking about after you correct it with the capacitor not before? The wording made it seem as if it is already at unity which made no sense to me. So basically, I have to find the power factor before the capacitor is added...
22. ### Power Correction Unity

1. Homework Statement Not sure if this is the correct place for Electrical Engineering Homework help but here goes A single-phased motor connected across a 240-V source at 50Hz as shown in the figure has a power factor of 1.0, I = 20A, I1 = 25 A. Find the capacitance required to give a unity...
23. ### Frequency of gears (given frequency of shaft)

Considering just a single gear, you're saying the tangential velocity is different at every point? How is that possible when ω and r are both constant? These only show me calculations when I know the teeth of the gears. In this problem, I don't know the teeth.
24. ### Frequency of gears (given frequency of shaft)

In order to find frequency, I took the tangential velocity of shaft AB and set it equal to shaft CD so that (2πfAB)rB = (2πfCD)rC. Then the 2π cancels out and I'm left with a relationship between just the gear radius and frequency (fAB)rB = (fCD)rC . Which would mean that shaft AB frequency of...
25. ### Frequency of gears (given frequency of shaft)

1. Homework Statement 2. Homework Equations tangential velocity v = ωr angular velocity ω = 2πf 3. The Attempt at a Solution Not really looking for help to solve the problem. I'm just confused about the speed/angular velocity and frequency If the frequency of the motor is given as 24...
26. ### Theorems of Pappus (Finding mass)

By "shaded area", they mean the cross-hatched section right? Wouldn't that make the half circle area void as well? edit: never mind I get what you're saying. Thanks lol. The volume of only the cross hatched section means obtaining that area and coordinate only. Which means I have to subtract...
27. ### Theorems of Pappus (Finding mass)

1. Homework Statement A steel die, shown in section, has the form of a solid generated by revolving the shaded area around the z-axis. Calculate the mass m of the die. 2. Homework Equations V =θ(rA) where r is the distance from the origin to the centroid of each shape m = ρV where ρ =...
28. ### Falling Through Earth's Center

Well that's great -__-. Also, if I use the conservation of energy, I still get v = √(2aR) but I don't understand how to solve it the same way my book wants me to. Using W = ΔK where K initial = 0 and so W = K final = 0.5m(vf)^2. If W = ∫ F dr, then what is F? Am I supposed to use F =...
29. ### Falling Through Earth's Center

How come the book uses the same value for their calculation then?
30. ### Falling Through Earth's Center

1. Homework Statement With what speed would mail pass through the center of earth if falling in a tunnel through the center? 2. Homework Equations W = -K K = 0.5mv^2 (vf)^2 = (vi)^2 + 2aΔx 3. The Attempt at a Solution My main question is why can't I use the last equation...