Rod Definition and 1000 Threads

  1. LCSphysicist

    Solving Waves on a Metal Rod with kx + Φ

    I am trying to solve this question by ξ = A*cos(ωt + θ)*sin(kx + Φ) Anyway, the two initial terms of the product helps nothing (i think), what matters is sin(kx + Φ) So, i tried by two ways: First: The stress is essentially zero on the ends, that is, something like cte*∂ξ/∂x (strain) would be...
  2. Nexus99

    What is the correct expression for the total moment of inertia in this scenario?

    1) I found: ##x_{CM} = z_{CM} = 0 ## ##y_{CM} = \frac{L}{2} \frac{m_1 - m_2}{M + m_1 + m_2} ## 2) Applying the conservation of linear momentum: ##M v_0 - m_1 v_0 - m_2 v_0 = (M + m_1 + m_2) v_f ## ##v_f = \frac{M - m_1 - m_2 }{M + m_1 + m_2} v_0 ## The velocity should have been found also...
  3. cwill53

    How much ice is needed to cool 31055.04J of water from 42°C to 0°C?

    My answer: a. $$H=\frac{dQ}{dt}$$ $$H_{brass}=H_{copper}$$ $$(109\frac{W}{m\cdot K})(0.005m^2)\frac{100^{\circ}C-T_{c}}{0.3m}=(385\frac{W}{m\cdot K})(0.005m^2)\frac{T_{H}-0^{\circ}C}{0.8m}$$ $$T_{H,Cu}=T_{C,brass}=T_{2}$$ $$-1.8166667T_{2}+181.666667^{\circ}C=2.40625T_{2}\Rightarrow...
  4. Nexus99

    A falling rotating rod strikes a ball of mass M....

    A homogeneous rod of length l and mass m is free to rotate in a vertical plane around a point A, the constraint is without friction. Initially the rod is stopped in the position of unstable equilibrium, therefore it begins to fall rotating around A and hits, after a rotation of ## \pi ## , a...
  5. Nexus99

    Rod on a Plane: Calculating Angular and Linear Motion After Impact"

    A hollow rod closed at the ends A and B, has mass M and length R. The rod is free to rotate on a horizontal frictionless plane around the z axis passing through A and coming out of the sheet. A body can slide without friction inside the cavity point mass m. Initially the rod is stationary and...
  6. C

    Finding the angular speed of a hinged rod without using torque or acceleration.

    The centre of mass of the rod would be at the middle of the rod i.e. at l/2=[50*10^(-2)]/2 The force responsible for torque will be acting downwards = mg The Torque = mg*l/2*sin(30) =mg*l/4 We know that Torque=I*alpha Hence alpha = mg*l/(4*I) Moment of inertia of rod about the end= ml^2/12 +...
  7. P

    Electric field due to a straight rod

    The net electric field is ## 2dE \cos\theta ## ## dE = \lambda dx/(4\pi\epsilon (x^2 +r^2)) \\ 2dE \cos\theta = 2r\lambda dx /(4\pi\epsilon (x^2 +r^2)^\frac 3 2) \\ E_{net} = 2\lambda r /(4\pi\epsilon) \int_0^a dx /( (x^2 +r^2)^\frac 3 2) \\ E_{net} = 2\lambda r /(4\pi\epsilon) [\frac x...
  8. cwill53

    Understanding Mean Force in Tandem Steam Engines

    I found the correct solution using the equation that relates force and pressure, but I don't REALLY understand what the question is asking and what is actually going on in the machine. I want a better understanding of everything that's going on, not just an answer. Below is a clear diagram and a...
  9. Adesh

    What force will be felt by ##B## when a rod is rotated?

    We have a rod ##AB## of mass ##m##, a force (perpendicular to AB) is applied at ##A##. I want to know how much force will ##B## going to feel? When ##F_1## is applied at ##A## rod will rotate about its COM (which lies at the Center) and hence the point ##B## will also move (a little downwards...
  10. V

    Calculate the center of mass of a non-uniform metal rod

    I know that if they had the same density they would have the center of mass at 1,5 m. But now that they don't the center of mass will be shifted towards the part of the rod with higher density. they will have their center of mass where they have equal mass p1*v=p2*v now i don't know how to...
  11. P

    Gauss' Law question about a conducting rod

    This is my attempt, i am confused at some points a. r = 0; The Electric field is 0 b. At r = a/2.00; I verified the answer and it is non zero, but my understanding is that the net charge should be on the surface of the conductor. Hence the charge q1=5*10^-15 C, should go to the surface of the...
  12. M

    Engineering Mechanical Vibrations - 2 DOF System - Rod with 2 springs

    Hi, So the question is to: derive the equations of motion for the following in terms of x1 and x2? The bar is assumed to be light and rigid. (NB. I know I posted another vibrations problem earlier in which I tried to use an energy approach to get to the equations of motion. However, we haven't...
  13. Eggue

    Angular momentum of a system of a rotating rod and sliding rings

    I got the correct answer for the first part but I'm not sure why the answer for (b) is the same for (a). Wouldn't the rings falling off mean that I_f = \frac{1}{12}M_L L^2 only where I_F, M_L, L are the final moment of inertia, mass of the rod and length of the rod as opposed to I_f =...
  14. alexm

    Motion of rotating rig, find the angle variation with control rod length

    Summary:: We have a rotating arm, offset from the centre of rotation by a certain length, which is controlled by varying the length of a control rod. Need the angle of the rotating arm in terms of length of the rod. The blue line is a fixed column structure. CE and BD form the rotational...
  15. Eggue

    Moment of inertia of a rod bent into a square

    I tried to find the moment of inertia of 2 rods connected at the corners by adding up their moments of inertia: \frac{1}{3}(\frac{M}{4})a^2 + \frac{1}{3}(\frac{M}{4})a^2 = \frac{1}{6}Ma^2 I then tried to solve for the moment of inertia at the center of mass of the 2 rods using the parallel...
  16. rdchin71

    I Exploring Fishing Rod Weight and Casting Distance: A Newbie's Question

    Hello, I am new to this forum. I have a question, hope I'll find some answers here. My question is - if there are 2 fishing rod, one lighter (physical weight) than the other. Will the lighter fishing rod cast a lure/bait further than the heavier fishing rod, assuming the rod length...
  17. R

    A doubt on Electrostatics -- An electrified rod attracting light objects

    "When electrified rods are brought near light objects, a similar effect takes place. The rods induce opposite charges on the near surfaces of the objects and similar charges move to the farther side of the object." -from a high school physics book. NCERT Class 12th part 1 to be precise. can...
  18. M

    Velocity / Acceleration Diagrams of a Mechanism - Piston and a rotating rod

    Summary:: This is a question about finding the acceleration of a point in a mechanism Hi, I have a question about the mechanism shown in the attached picture: Question: We are told that \omega = 6 rad/s and the first part is asking me to find the acceleration of point P on the piston when...
  19. Like Tony Stark

    Why Is the Reaction Force Inclined in One Case but Perpendicular in Another?

    Hi, I have a doubt about reaction forces... I've attached a picture that shows two similar situations. The first one shows a rod left with an angle ##\beta## while it is on a smooth surface. The second one shows a rod leaning on a smooth surface and wall. My question is: why is the reaction...
  20. J

    Motion of 2 masses connected by a rod to a pendulum

    I am not sure which other forces I should consider besides those 3. I cannot consider tensions due to the massless rod on the masses since those will not add up to zero.
  21. physics_CD

    A cart with two cylindrical wheels connected by a rod

    Firstly I only consider one of the wheels. This wheel consists of a big wheel (black) with mass M and radius R and inside it a circular region with a negative mass (-m) and radius R/2. (I assume they have same mass density but with opposite signs. I do this because I don't know where the center...
  22. Like Tony Stark

    Determine tensor of inertia of a rod

    I have to find the inertia tensor of these rods and I don't have the concept that clear... I mean, I know the formulas like: ##I_{xx}=\int y^2 + z^2 dm## ##I_{xy}=\int xy dm## But I don't know what ##x, y, z, dm## stand for. In other words, I don't know what I should replace in the formula...
  23. Ibix

    A Stress-energy tensor of a rotating rod

    A rod rotates freely (edit: about an axis perpendicular to its length) in empty space. Working in an inertial coordinate system where the rod rotates around a fixed point, the rod is straight, of length ##2L## in its spinning state, and its mass distribution is symmetric along its length. The...
  24. Nacho_rc11

    Rotational dynamics: Rotating rod with two attached balls about a non principal axis

    Firstly I deduced that in this situation the moment of inertia I, is not going to be parallel to w. And I calculated it as a matter of the angle, for the rod and the two point particles attached (with a mass 'm'), and the total moment of Inertia ended up being: I=((R²*sin²α)/2)*(M/6 + m) Being...
  25. A

    Possibility of turning a threaded rod with spur gears using a motor

    So I'm a college student currently doing A-Level Physics, I am attempting to build a type 4 double arm barn door tracker and although it has been a complicated project, I believe I've got all the planning done, however, I have a 2Rpm motor, a PWM motor controller, 2 9v batteries, an M8 threaded...
  26. barryj

    Linear and angular momentum problem: Ball hitting a rod

    Homework Statement:: Ball of mass mb and velocity vb hits rod of length L , Rod pivots about the center. What is the angular momentum aafter impact? Homework Equations:: I = 1/12 (mR^2) I = mR^2 See the attached figure. I understand the concept of linear and angular momentum separately but I...
  27. isabelle3

    A bullet hits a rod attached to a pivot at one of its ends....

    My initial thought was to use the conservation of energy law since there're no external forces acting on the system bullet + rod. The rod is in rest, the bullet is moving. Then after the collision, the bullet and the rod are rotating around the pivot together, so the kinetic energy of the bullet...
  28. R

    Is the Stress in a Twisted Helical Spring Caused by Torsion or Bending?

    Let us consider the massless homogeneous helical spring with the infinitesimal wire diameter d and wire length l. We denote the spring radius as R. Now we consider the curvilinear spring section of length dl. We draw radii from the spiral axis to the centers of the end cross-sections of this...
  29. A

    Kinematics and angular speed of a collision between a rod and puck

    initial total KE= (1/2)(0.6kg)(8m/s)^2 = 19.2J (0.6kg)(8m/s) = (0.6kg+1.8kg)(vf) vf= 2m/s final KE= (1/2)(0.6kg+1.8kg)(2m/s)^2 = 4.8J I tried to use linear speed=angular speed * radius : thus 2m/s= angular speed * (3.3m/2) angular speed= 1.2 rad/s Apparently that is wrong.
  30. Santilopez10

    Sign Convention for Angular Acceleration in Rotational Motion

    we know that the center of instantaneous 0 velocity lies in the interception of 2 perpendicular lines to 2 points, which in this case lies above B. The velocity of any point of the rod can be described relative to the center of instantaneuous 0 velocity ##(Q)## as: $$\vec v_{P/Q}=\vec \omega...
  31. dlxgains

    Moment of inertia project help- experiment 1: Bifiler Rod

    Homework Statement: So i need to find equations to help me with a bifiler suspension experiment in which i will use a rectangular drop bar as the oscillating object, also any help with the method of this experiment would be greatly appreciated. The end goal is to find the moment of inertia...
  32. A

    Rotational torque and kinematics of a rod

    moment of inertia = (1/3) (2.1kg) (1.2m)^2 = 1.0 kgm^2 center of mass= (0.6i, 0j) magnitude of the gravitational torque=9.8m/s^2*2.1kg*0.6m= 12.34N*m position of the new center of mass now : x direction = cos(20)*0.6m=0.56m y direction= -sin(20) * 0.6m = -0.2m change in gravitational...
  33. Kaushik

    Tension of a rod rotating on a horizontal table about a vertical axis

    If a rod is on a table (horizontally) and rotating about an axis that passes through one of its ends and vertical to the table, what would be the tension on the opposite end of the rod (the end opposite to the axis) . In this post (Check this post out from Socratic QnA), the limits take while...
  34. ?

    I How specifically does an accelerated uniform rod Lorentz contract?

    I am trying to push the boundaries of special relativity with a self-imposed challenge problem. A common derivation of relativistic kinetic energy involves an object to which a constant force is applied. I want to consider a similar scenario, but instead of a point object we now have a uniform...
  35. A

    Torque and inertia of a wooden rod

    ∫ λ(x)=0.2 kg/m + 0.061(x/L)^2 kg/m = 0.2(x) + (0.061/3) (x^3) /(1/L^2) mass of rod = 0.2+ (0.061/3) =0.22 kg inertia of rod through nail = (1/3) (mass) (L)^2 inertia of rod through nail = (1/3) (0.22kg) (1m)^2 = 0.073 kg*m^2 torque magnitude = (53N) (0.5m) = 26.5N*m angular...
  36. brotherbobby

    Is the Calculation for the Center of Gravity of Two Spheres and a Rod Correct?

    I begin by drawing the problem. Let the center of the bigger sphere on the left by the origin for the system. Calculating ##x_C = \frac{10 \times 1.1 + 20 \times 2.15}{50+20+10} = \frac{54}{80} = 0.675\; \text{m} \;= \boxed{67.5 \; \text{cm}}\;##. Problem is, doesn't match the answer in the...
  37. Kaushik

    A uniform rod allowed to rotate about an axis and then it breaks

    A uniform rod AB of length ℓ is free to rotate about a horizontal axis passing through A. The rod is released from rest from the horizontal position. If the rod gets broken at midpoint C when it becomes vertical, then just after breaking of the rod. Choose multiple answeres from the below...
  38. brotherbobby

    Tension in a rotating rod at various places

    (The answer given in the text says ##\boxed{T_1\; >\; T_2}## but, as I show below, I think it's just the opposite). I begin by putting an image relevant to the problem above. Taking a small particle each of the same mass ##m## at the two positions, the centripetal forces are ##T_1 =...
  39. jisbon

    Electric forces between conducting rod and rail

    Alright, to start off: I'm not even sure how this works in the first place. What I do understand is that if they carry current in the opposite direction, using right-hand grip rule, the magnetic field between them will be the same (into the page). Hence using the left-hand rule, I can deduce...
  40. M

    Calculate linear charge density of rod & mag. of E-field at point

    Here is my work done for this problem, along with a diagram of the situation. I'm not worried so much about the arithmetic because our tests are only 50 min long so the problems they give us do not require heavy integration or calculus, but you need to know what goes where in the formula. That...
  41. D

    Electromotive force induced in a conducting rod

    i don't understand why in the solution of this exercise, the induced electromotive force / current is counterclockwise. Shouldn't it be clockwise? ##emf=-\frac {d \Phi_B} {dt} ## According to the picture the rod is moving upward, the magnetic flux (entering the page) is decreasing due to a...
  42. D

    The Magnitude of Induced EMF in a Moving Rod?

    Homework Statement: A 25.0 cm long metal rod lies in the xy-plane and makes an angle of 36.9 with the positive x-axis and an angle of 53.1 with the positive y-axis. the rod is moving in the +x-direction with a speed of 6.80 m/s. the rod is in a uniform magnetic field B=...
  43. B

    B Rod Dipping in a Black Hole: Exploring Tidal Forces and Event Horizon Impact

    if there's a really good rocket hovering just above a super massive black hole with very low tidal force, and it dips a rod just inside the event horizon, will the rod break? it seems a certainly but the tidal forces are very weak. is it like dipping ur feet into piranha infested water? so when...
  44. Homgkung

    Can we find the frequency of a rod pendulum by just using F=ma?

    Summary: When I tried to find the angular frequency of a rod pendulum, I attempted to find its angular acceleration first, however, I realized that the results are different by using different approaches. i.e. (1) Newton's second law for a system of particles (2) Newton's second law for...
  45. Physics lover

    EMF induced in a rotating rod having mass

    I first calculated induced emf and then calculated torque about O.But what will i do further.I think i need to find current and then fidn emf=IR. Help please.
  46. naji0044

    Rotational inertia - globes connected by a thin rod

    Problem Statement: Finding the rotational inertia Relevant Equations: I=∑m*r^2 A rigid body of 2 massive globes with homogenous mass distribution and a thin rod is connecting the 2 globes. The globes has radius R1 = 0.18 m and R2 =0.28 m and masses m1=193 kg and m2=726 kg. The thin rod has...
  47. resurgance2001

    Rod resting on a cylinder, find mu

    My solution is on the files. The basic approac was the take moments about A. Then find the reaction at C. Use the reaction at C to find the friction between rod and cylinder. I take it to mean from the question that the friction between the rod and plane is equal to the friction between...
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