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  1. K

    Diffusion or turbulence?

    <Mentor moved to Physics> My teacher talks about turbulence (2D and 3D), but I don't quite understand this. How is the turbulence different in the two buckets, and why does my teacher talk about turbulence but not diffusion? Is not diffusion the reason why the dye spreads in the water? I have...
  2. K

    What does it mean that a rigid body is in equilibrium?

    So I have always been thinking that equilibrium means that an object is not moving or having constant acceleration. On a webside they said: " A rigid body is in equilibrium when it is not undergoing a change in rotational or translational motion. " To me it sounds like the object then must not...
  3. K

    Buoyancy force when a ramp is under water

    So I have made force diagram And I think that I should find the acceleration by using these equations: ##\sum Fx=w\sin(15)-f_k-T_{x-buoyancy} ## ##\sum F_y=N+T_{y-buouancy}-w ## I know that the volume of water displaced must be ##V=\frac{1}{2400}m^3## and the mass of the water is then...
  4. K

    Help with understanding this rigid-body equilibrium problem

    So here are two problems I have been working with lately: I have solved both, so I don't need the help to find the answers. The thing that confusses me is which object one should choose to apply the equations above. When it comes to the first problem, we apply the equations to the pole, but...
  5. K

    When does an object have kinetic rotational energy?

    When does an object have rotational energy? Is it only if it rotates around an axis within the object? Does for example a ball attached to a string with a uniform circular movement have rotational kinetic energy?
  6. K

    Projectile-car system and momentum

    I have done question 1. But I'm struggling with the other one. So since the only thing I know about the rocket is the mass and the velocity, I guess I have to use momentum to solve this problem. From the first question, I found out that the x-velocity of the projectile is ##v_x=5...
  7. K

    Understanding rigid-body equilibrium problem

    So I have this problem The soultion to the problem gives me this drawing But I don't understand what ##F_h## and ##F_v## is
  8. K

    Help with understanding this momentum problem

    Solution on the link:
  9. K

    Help with acceleration -- A block on top of a block on a frictionless table

    I don't understand the problem. Does not block A and B make a system, so they should have the same velocity and acceleration at all time? If not, why do they have different accelerations? I don't understand this part of the problem either: "pull applied to block B equals 12.0 N, then block B has...
  10. K

    Average speed and average velocity

    So thing that confusses me, is what is the difference regarding the calculation of speed and velocity? In think I should use the formula I wrote above to find the average velocity, but I don't understand what the formula for average speed will be then. By the way, when using the formula above...
  11. K

    I Riemann integrability with a discontinuity

    So, I know that a function is integrable on an interval [a,b] if ##U(f,P_n)-L(f,P_n)<\epsilon ## So I find ##U(f,P_n## and ##L(f,P_n## ##L(f,P_n)=5(3-\frac{1}{n}-0)+5(3+\frac{1}{n}-(3-\frac{1}{n}))+7(4-(3+\frac{1}{n}))=22-\frac{2}{n} ##...
  12. K

    Static friction — Experiment pulling different blocks across a surface

    I know that I am supposed to use the equation I wrote, but how do I find the maximum force of static friction and coeffcient of static friction if none of them are given beforehand? I can't have to unknowns in an equation. We then did the same thing, the only difference was then to measure the...
  13. K

    Price and Merit order

    An isolated island has a specific electricity demand of 75 MW for a specific hour. The power producers have made the following offers during the hour: To be honest, I don't understand both a and b. When it comes to a, should I just use several of the options in the table to get 75 MW? Or should...
  14. K

    How to use Weibull distribution when it comes to wind?

    I know that I'm supposed to use Weibull, but why does my teacher take the middle value, 5 m/s? Should one not integrate the formula and the use 4,5 and 5,5 as limits? This is what he has done: He then writes: makes a guess of an interval of 1 m/s and get: To be honest, I really don't...
  15. K

    Does someone understand this picture? (Solar heating)

    Homework Statement:: I'm working with solar heating systems, and my teacher added this picture to his PowerPoint. But I don't understand the picture. Could someone help me? Homework Equations:: The only thing I understand is that ##I_0## is the energy from the sun. But the other arrows confuse...
  16. K

    Help with understanding difference between these codes

    #Code nr.1 x=[1,2] def double(l): return [a*2 for a in l] double(x) print(x) #Code nr.2 def f(x): x[0]=x[0]+1 return x x=[3] f(x) print(x)
  17. K

    Differential equation problem: Modeling the spread of a rumor on campus

    So this is what I have done: ##f'(t)=k*f(t)*(A-f(t))*(1-sin(\frac{pi*x}{12}))## ##\frac{1}{f(t)*(A-f(t))}=k*(1-sin(\frac{pi*x}{12}))## I see that the left can be written as this (using partial fractions): ##1/A(\frac{1}{f(t)}-\frac{1}{A-f(t)})## And then I take the integral on both sides and...
  18. K

    Piecewise function

    a) At which intervals are f strictly increasing and at what intervals are f strictly decreasing. Should I just find the derivative of both of the functions? If so, I get that the function is increasing at the intervals (−∞,0) and (0,∞). Is this right, or can I just say that the function is...
  19. K

    If possible, find a and b

    So this is what I'm thinking: After watching some YouTube videos on the subject, the first thing I do is check for continuity. So I plug in for ## x=0## and is left with ## \frac{e^{b}-1}{0}=1##. I don't think I'm doing this right given the fact that I'm left with 0 in the denominator...
  20. K

    Help with making a function

    Ok. So if i sketch the curve I can see that this pound has a shape of a square. Ann and KFC has the same distance from the pond. I'm able to calculate the time for Ann to walk around the pond, and if she walks in a straight line from where she stands to KFC. If she walks around it will take...
  21. K

    List with lists in Python

    I have a list containing several lists with two elements each. I want to multiply the last element in the inner lists with a number x, and then print the new list. How do I do this?
  22. K

    Curve sketching

    1.Prove that f'(x) is strictly decreasing at (- ##\infty##,a) and strictly increasing at (a,##\infty##). 2.Prove that f'(x) has exactly two roots. I tried to find f''(x)=0, but I'm not able to solve the equation. What should I do?
  23. K

    Help with an epsilon-delta proof

    I have been struggling with this problem and also my friends. We are not the best at epsilon-delta proof and we have not found an understandable solution to this problem.
  24. K

    Help with limits and a derivative

    I don't understand my textbook, so I simply don't understand how to solve this math problem. I really appreciate some help!
  25. K

    Help with L'Hôpital's rule

    My attempt: ##\frac{f'(a)}{g'(a)} ## = ##\lim_{h\to 0}\frac{f(a+h)-f(a)}{h}\cdot\frac{h}{g(a+h)-g(a)}## = ##\lim_{h\to 0}\frac{f(a+h)-f(a)}{g(a+h)-g(a)}## I don't think I am doing this right. I don't even understand how I am supposed to use the boundary rules. I really appreciate some help!
  26. K

    Iterative derivatives of log

    I have never used induction to justify the derivative to a function, so I don't know where to start. Does anyone have some tips?
  27. K

    Can somone help me with vectors?

    Homework Statement A tent with no bottom stands in a terrain. The tent has three rods that are gathered in T = (1,1,4). The tent bars stands in the points A = (0,0,0), B = (3,1,1) and C = (- 1,3,2). The tent must be supported by an additional rod which is in a point D and attached to T. The rod...
  28. K

    Trig problem involving a triangle's angles and sides

    Homework Statement In the triangle ABC, angle A = 30 deg, angle B = 45 deg and since AC = a. The perpendicular from C on AB cuts AB in E. In this task you should calculate exact values. a) Determine AE, BC and AB expressed by a. b) Perpendicular from B on AC intersects the extension of AC in...
  29. K

    Redox titration

    Cl2(g) + 2I–(aq) -->I2(aq) + 2Cl–(aq) (reaction 1) [2S2O3^(2-)(aq) + I2(aq) --> S4O6(2-)(aq) + 2I–(aq) (reaction 2) Why isn't n(I2)(reaction 2)=2n(S2O3^(2-))(reaction 2). I don't see why this is wrong. <edit: remove size and italics>
  30. K

    I need some help with integrals

    Homework Statement You are given the function f(x)=3x^2-4x-8 a) Find the values of a. Explain the answers using the function. Homework Equations The Attempt at a Solution a^3-2*a^2-8*a=0 a=-2 v a=0 v a=4 I found the answers, but I don't know how to explain my answers by using the...