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1. I Force Generated By Leg Muscles in Free Body Diagrams

Ok, so I guess I am asking what force causes the force of the leg muscle onto the foot and since it is an internal force, what is the reaction force to that force?
2. I Force Generated By Leg Muscles in Free Body Diagrams

Suppose a person is walking on the ground without slipping. For the free body diagram of just the person, only the frictional force is drawn in the horizontal direction. The force exerted by the leg muscles to generate a force against the ground is considered an internal force. What would be the...
3. Engineering Derive the governing equation for the voltage Vc across the capacitor

I don't understand. I drew the circle and currents in blue below:
4. Engineering Derive the governing equation for the voltage Vc across the capacitor

Can you explain explicitly? I still believe there can be current from a to b...
5. Engineering Derive the governing equation for the voltage Vc across the capacitor

I still don't understand why the current in the middle is zero....if I do KCL at point a or b, it seems like there could be current there....
6. Engineering Derive the governing equation for the voltage Vc across the capacitor

I think it can though...why can it not?
7. Engineering Derive the governing equation for the voltage Vc across the capacitor

I only know Vc = 3 V; I_L =0.0015 A for t < 0
8. Engineering Derive the governing equation for the voltage Vc across the capacitor

I don't know if the resistors have the same current -- that is just an attempt of mine. In fact I think the resistors might have different current.
9. Engineering Derive the governing equation for the voltage Vc across the capacitor

Yeah, I meant KVL: -5 + Ic*2*10^3 + Ic*10^3 = -Vc I know what part a is. I am wondering about part b.
10. Engineering Derive the governing equation for the voltage Vc across the capacitor

I was thinking about doing KVL around the circuit at the right but I noticed when the switch opens, the current through the circuit at the right is not the same throughout -5 + Ic*2*1-^3 + Ic*10^3 = -Vc Ic is not the same around the right circuit so I am stuck....
11. Engineering Short vs Open Circuit: Is That Correct?

Ok, I wrote my equations wrong initially. But I am wondering what frequency is the impedance an open circuit? The impedance would have to equal infinite?
12. Engineering Short vs Open Circuit: Is That Correct?

For the first circuit, Req = ZL + ZC = -j/(w*C) + j*w*L = 0 for short circuit, so w = 0? For the open circuit case, -j/(w*C) + j*w*L = infinity, so w = infinity? Is that correct?
13. Energy conservation law question with capacitor

Does the work energy theorem: delta W = delta KE apply with external and nonconservative forces as well or does that formula only work if there are only conservative forces and external forces = 0?
14. Energy conservation law question with capacitor

Ok, I had a follow up question. How come in the work energy theorem, work = change in kinetic energy; but in the energy conservation law work = change in kinetic energy + change in potential energy?
15. Energy conservation law question with capacitor

I was wondering why energy of capacitor does not equal change in kinetic energy PLUS change in potential energy where potential energy is the change in the potential energy of the charges. I believe that should be so because energy conservation = change in kinetic energy plus change in potential...
16. What does weak chemisorption mean?

I am reading a research paper that says weak chemisorption of silver with olefins basically means more effective olefin/paraffin separation. If silver weakly binds to olefins, wouldn't that make a lousy separator?
17. I Finding the center of area (centroid) of a right triangle

Yes off by a factor of two. Can you explain that more clearly? What do you mean by "instead of the height of the strip's centroid halfway up?"
18. I Finding the center of area (centroid) of a right triangle

$$x(y) = b - y\frac{b}{h}$$ $$y(x) = \frac{-h}{b}x +h$$ No they would be different because $$\int_{0}^{h} y*x(y)dy = \int_{0}^{h} y*(b - y\frac{b}{h})dy$$ this does not equal $$\int_{0}^{b} y(x)*y(x)dx = \int_{0}^{b} (\frac{-h}{b}x +h)^2 dx$$
19. I Finding the center of area (centroid) of a right triangle

To find the y value of the centroid of a right triangle we do $$\frac{\int_{0}^{h} ydA}{\int dA} = \frac{\int_{0}^{h} yxdy}{\int dA}$$ What is wrong with using $$\int_{0}^{h} ydA = \int_{0}^{b} y*ydx$$ as the numerator value instead especially since ydx and xdy are equal and where h is height of...
20. I The speed of a waves on a string in Simple harmonic motion

Ok, not sure how the tension in the x direction can be approximated as the resultant tension
21. I The speed of a waves on a string in Simple harmonic motion

Yes, this makes the tension of the string in the horizontal direction as well
22. I The speed of a waves on a string in Simple harmonic motion

Yes, I know that F is the tension but is F the tension of the string in the x direction or is F the tension that is tangent to the string. My book derives it like this, implying that F is the tension of the string in the x direction
23. I The speed of a waves on a string in Simple harmonic motion

The speed of a wave in simple harmonic motion on a string is $$v= \sqrt{\frac{F}{\mu}}$$ where v= the horizontal velocity of the wave on a string. Is the F the horizontal force or the resultant force (combination of Fy and Fx)?
24. Can this system of inequalities be solved for x?

That is solving it graphically. I would like to solve it algebraically.
25. Can this system of inequalities be solved for x?

Summary: Can these two equations be solved for x like a system of linear inequalities, and how? ##x- 2y \le 54## ##x + y \ge 93## We start with ##x- 2y \le 54## ##x + y \ge 93## Multiplying the second equation by 2, we have ##2x + 2y \ge 184##. We cannot seem to cancel the y out with the...
26. I Translational force of a pulley

So with weights on either end of the red string, it would be (M+m + Weights)g?
27. I Translational force of a pulley

What about "I am wondering how come you are dividing the tensions into 0<ϕ<π/2 and π/2<ϕ<π. I interpreted the tension being 20 N - 60 N at all infinitesimal points around the pulley." So is ##dl = -R\sin\phi d\phi \vec i + R\cos\phi d\phi \vec j## or ##-\sin\phi\hat xdx+\cos\phi\hat ydy =...
28. I Translational force of a pulley

Not translational is rotational force
29. I Translational force of a pulley

Translational is the force in the x and y directions.
30. I Translational force of a pulley

I am wondering how come you are dividing the tensions into ##0<\phi<\frac{\pi}{2}## and ## \frac{\pi}{2}<\phi<\pi##. I interpreted the tension being 20 N - 60 N at all infinitesimal points around the pulley. Also I do not understand why we have to multiply by dl in ##d\vec{T}=20d\vec{l}##...
31. I Translational force of a pulley

If that's the total torque how come a lot of the videos show torque in my example as 20r - 60r where r is the radius of the pulley? Source:
32. I Translational force of a pulley

I just want the translational force of the pulley and am not sure if to calculate the translation force of the pulley I would have to consider all the forces at all the points along the circumference
33. I Translational force of a pulley

Would just -20 - 60 - Mg + B = 0 be enough?
34. I Translational force of a pulley

How do you draw the triangle?
35. I Translational force of a pulley

Below is a pulley with mass and a string around it where the tension of one end of the string is 20 N and the tension of the other end of the string is 60 N. I know there is a net torque due to the differing tensions of the string, so I am wondering what the translational forces are on the...
36. B Conservation of momentum and conservation of energy details

So you're saying the equation should beJ = ## \int_{t1}^{t2}(-k{x(t)})dt## where k is the spring constant of the ball, and x(t) the ball's compression?
37. B Conservation of momentum and conservation of energy details

So the force exerted on the ball by the ground equals the force exerted by the ball on the ground, so we were just talking about a sign difference? So then if the impulse is the force exerted on the ball by the ground, J = ##\int_{t1}^{t2}(k_2{x_2(t)})dt##, where ##k_2## is the spring constant...
38. B Conservation of momentum and conservation of energy details

According to my class notes, the impulse (change in momentum) for the ball, is just the force the ball exerts on the ground integrated for a certain time duration.
39. B Conservation of momentum and conservation of energy details

Yes. I am talking about an elastic scenario. In scenario 2, would the impulse = ##\int_{t1}^{t2}(0.5k{x(t)}^2 + 0.5k_2{x_2(t)}^2)dt## or just J = ##\int_{t1}^{t2}(0.5k{x(t)}^2)dt## where k is the spring constant of the ball, and x(t) is the ball's compression, or should it be ##k_2## the spring...
40. B Conservation of momentum and conservation of energy details

For conservation of mechanical energy for dropping a ball on the ground, I have 3 scenarios for conservation of energy: 1) For the scenario right before the ball hits the ground ##mgh = 0.5mv^2## 2) For the scenario while the ball hits the ground using the potential spring force of the ball and...
41. B Conservation of momentum and conservation of energy details

Ok, got it. My last question was if there were an external force that caused the ball to drop with initial velocity v, would conservation of energy still be applicable since there was an external force? Or would the conservation of energy be applicable only after the external force stopped...
42. B Conservation of momentum and conservation of energy details

What if 2 balls collide each with mass m, one with initial velocity and one at rest, and both end up with 0 velocity. The conservation of momentum doesn't make sense like this: mv = 0. How come?
43. B Conservation of momentum and conservation of energy details

So if there is nothing moving after the collision, momentum is not conserved? Is there an external force (since that is when momentum is not conserved)?
44. B Conservation of momentum and conservation of energy details

Yes you are understanding me properly. Conservation of energy doesn't work which makes sense, but conservation of momentum does not work either in a case where the ball is dropped with a certain velocity and collides with the floor with 0 velocity, mv = 0... how come?
45. B Conservation of momentum and conservation of energy details

No, that is not what I mean. In my conservation of energy problem, I am setting the ground with height h = 0; If we have a ball dropped with height h > 0, the initial energy state is mgh. I want the final energy state to be when the ball hits the floor at 0 velocity, so the final energy state is...
46. B Conservation of momentum and conservation of energy details

Ok, but I would like to understand why it violates conservation of momentum. Is there a net external force? What is the external force? Is it the frictional force? But the frictional force between the 2 masses exists in inelastic collisions as well (which does have momentum conserved)
47. B Conservation of momentum and conservation of energy details

For my momentum example, I am talking about one mass colliding with another mass at rest and both having 0 velocities after the collision
48. B Conservation of momentum and conservation of energy details

If we have a ball with mass m dropped from a height h down to the ground, how come we can't set the conservation of energy equation just as the velocity of the ball turns 0. mgh = 0 If instead the ball were moving with an initial velocity v, would the equation be ##mgh + \frac{1}{2}mv^2 = 0##...
49. How to Solve for Delta_h: A Math Question

Oh nvm. I found the derivation in the book and got the correct answer. Thanks anyways.
50. How to Solve for Delta_h: A Math Question

ok, I am rusty with my diff eq, I get ##0.9\frac{dv}{dt} + bv = mg##... and then what?