Forces Definition and 1000 Threads

  1. G

    How to find the forces in a particular framework of light rods

    Could I please ask for help in how to do this question. Is it in fact well formed, can it be solved as it is or do I need more information? Q. Find the external forces and the force in each rod in the following framework of light rods which is supported and A and C: So, I need to find Fa...
  2. A

    I Forces to move on the level versus up an inclined plane

    If on a flat ground, we exert a force F to move forward, then we go to an incline plane of theta degrees. Why wouldn't the force F2 to move up the incline plane with respect to ground be F2*cos(theta) = F --> F2 = F/cos(theta) disregarding the effects of gravity?
  3. Amphibia

    Forces on two different blocks with two pulleys

    I don't know what to do as I know the forces acting on it but not the scalar like I just don't understand the question with two different pulleys I know the tension same everywhere
  4. Y

    Forces applied to a block on a ramp

    hey I am really hope for some help becuase i don't know what I am doing wrong, the angle of the first part is 21.801. here is my solution i would like to know what I am doing wrong
  5. G

    To find the forces acting in a system in equilibrium

    Could I please ask where I have gone wrong with my reasoning in the following question: The answers in given in the book are: (1/2)W tan(Ө) W vertically (1/2)W tan(Ө) horizontally Here is my diagram: Considering the system as a whole: (In the text below "Ya" and "Xa" are the forces at...
  6. B

    B Can You Use a Rubber Bracelet as a Buoyancy Reference for Freediving?

    First of all, I'm new to the forum, and rather uneducated, so I apologize this is likely in the wrong section. I've recently (like last night lol) started looking into freediving. I haven't taken any classes or anything yet, so all of this might be common and answered there. However, one of...
  7. J

    A Generalized Forces and QED/QCD

    In Lagrangian mechanics we learn about generalized forces. However, I haven't seen these explicitly mentioned in books on QFT. Can the Lagrangians of QED or QCD be expressed in terms of generalized forces or is there some connection there, in particular to the Nielsen form.
  8. S

    Body forces in static equilibrium (FEM issue)

    Hi, I have an issue with understanding the body forces in the context of FEM simulations. I am using freefem to do the simulations. So I took a simple unit cube, fixed the displacements at side ##x=0## and prescribed a displacement ##u_x = 0.025## at ##x=1##. If required, the entire script is...
  9. SpectraPhy09

    Plotting the graph of Friction Force vs. time (Laws of motion)

    F.B.D Of first block (I have shown only the horizontal Forces) f1(max) = μ (1kg)(g) = 0.5 * 10 = 5N F.B.D Of the second Block f2(max) = μ (3kg)(g) = 15N Now the string will become taut and the tension will start acting when f = t = 5N But for 0<f<5N there will be no motion between the 1 kg...
  10. runningphysics

    Two forces acting on an object given in vectors - SOLVED

    I tried splitting the forces up into F1 and F2 making Newtons second law equation into F1+F2=ma. Then I added over the the first force given. multiply the mass to the acceleration terms to get F2= (m*ai + m*aj) - F1
  11. M

    I Unbalanced forces acting on a ball at maximum altitude

    When a ball projected vertically upright reaches its maximum height is it instantaneously stationery (calculus provides for instantaneous events) before it starts its downwards journey? is gravity acting on the object at that instant? Newton provides that an object at rest must be subject to...
  12. U

    Comparing hydrostatic forces at the bottom of these 3 containers

    hello all , 1st and 2 nd water containers sit on ground and 3rd type of water container sit on fixed support along X axis and bottom parts are suspended in air , pls see picture , the drawing is half cross sections of cylinders All water level heights H and tubes D diameter are same ...
  13. B

    B Forces on a passenger in a car?

    What would the forces acting only on a passenger in a car going at constant speed on a level surface be? Of course, there would be weight and the reactive force acting on any passenger, but is there a horizontal net force? Or are there just the forces acting on the car and there are no...
  14. Z

    Torque and forces (Beginner level)

    Summary:: I am trying to figure out how much force that either end of a tilted rod are subjected to as a consequence of gravity. One end being attached to a hinge, the other to a string from above. Hello, it's my first time on this forum. I have recently started learning about torque (Nm) and...
  15. Yossi33

    Forces that act on a physical pendulum

    hello, i have a question about the forces that act on a rod at it's pivot point. the rod is free to rotate about the pivot point at the edge and it starts from rest parallel to the ground.the question is : when it reach to angle theta find the a] the angular velocity b] angular acceleration c]...
  16. G

    To find direction and magnitude of forces acting in a system

    Please could I ask for help with the following: Here is my diagram, I show the rod displaced from the sphere so as to label the internal forces acting on each of the rod and the sphere: In the diagram below I have added the line through DE at angle ꞷ the the horizontal, and a few other...
  17. R

    I am calculating the forces on String cheese with net force = 0

    Here is the link to the question. https://www.khanacademy.org/science/physics/forces-Newtons-laws/Newtons-laws-of-motion/a/what-is-Newtons-second-law What is the magnitude of the force F1 ? What is the magnitude of the force F2 ? Here is my drawing I made At this step I am lost. ## ay...
  18. J

    A Problem solving forces with pressure integration

    Angle theta is different for every place at airfoil surface, so it can't be one theta from leading edge to trailing edge. Can please someone explain pressure integration in depth, step by step?
  19. K

    I Potentials of conservative forces

    Goldstein writes "only if ##V## is not an explicit function of time is the system conservative"That means ##V(r,\dot{r})## is a conservative potential, however I think that only potentials of the form ##V(r)## are conservative potentials. Could you please tell me where I'm going wrong. Thank you.
  20. J

    I Are Geometric Points Affected By Forces?

    Yesterday I found a playlist of videos by a youtuber "Dialect" who made a distinction between what he called Tier 1 and Tier 2 arguments of Relativity. Tier 2 promoted a view that acceleration was an observer dependent phenomena. In particular he was discussing the Twin Paradox, and he said...
  21. greg_rack

    Solving a Rod-Particle System: Troubles with Forces

    Hello guys, here's another problem I'm having troubles with(I have attached my working out not for laziness, but clarity since steps are many). I started by defining a polar coordinate system, and then drawing the FBD and KD to get to the equations of motion for particle P. I identified 3...
  22. greg_rack

    Solving a Problem: Forces Acting on P

    Hello guys, here's a problem which I'm having troubles solving. It asks for the forces acting on P when ##\theta=60^{\circ}##. I thought for this problem it would have been convenient to consider a polar reference system(r, theta). Drawing the FBD of pin P at a moment in time, we will have 3(?)...
  23. muna

    How Do Support Reactions Affect 2D Static Equilibrium in a Shopping Cart?

    Hey guys, help me out a bit here. I want to form 2d static equilibrium equations for a shopping cart. This is for an assignment. I'm kind of confused about the support reactions. I'm not sure how I should analyze the basket. I was going with A as a fixed support (see image) since I'm guessing...
  24. ergospherical

    I System, potential energy, and nonconservative forces: The whole story

    [Mentors' note: This thread was split off from https://www.physicsforums.com/threads/system-potential-energy-and-nonconservative-forces.1009237/] This is not a particularly helpful way to think about things; For a general mechanical system, you usually split the specified forces into external...
  25. Khalid Qasim

    Bernoulli’s Equation and External Forces

    Summary:: Bernoulli’s Equation and External Forces Hello all, I am a bit confused on this question: Water flows through a spray nozzle (as shown in the figure below) at a rate of 50 cm3 h -1 . The internal inlet diameter of the nozzle entrance is 5 cm and the internal exit diameter of the...
  26. F

    I System, potential energy, and nonconservative forces

    Hello, I am trying to get my head around the idea of nonconservative forces doing work and changing the potential energy of a system. First of all, forces acting on a system can be: a) internal and conservative b) internal and nonconservative (friction, pushes, pulls, thrust, etc.) c) external...
  27. SpectraPhy09

    Gravitational Forces between two masses

    Density of the Sphere = 3M/4πR³ Mass of carved out sphere = density × 4π/3 × R³/8 = M/8 The position of center of mass of The Sphere {M(0) - M/8(R/2)}/M-M/8 -R/14 So total distance between centers of the two bodies is R/14 + 3R = 43R/14 So now I found force between the Mass 7M/8 (left out...
  28. I

    Slider Crank Force Analysis: Understanding the Equilibrium Forces and Results

    I am in a mechanical design class that has been focusing on the slider crank mechanism. My professor tends to just provide derived equations without showing the analysis. I feel like I am missing out on some key understanding because of this. Specifically, I am trying to do what should be a...
  29. M

    Find Final Kinetic Energy of a particle subject to two forces

    I'm having trouble putting the rest of the equations together, I believe I need the different from (0,0,0) to (1,0,0) and then (1,0,0) to (1,1,0) right? Then solve for x direction and y direction. What would I use for Wnc tho? I'm very confused.
  30. H

    Forces and laws of motion -- Big gorilla hanging from two vines

    About 50 years ago, the San Diego Zoo, in California, had the largest gorilla on Earth: its mass was about 3.10 × 102 kg. Suppose a gorilla with this mass hangs from two vines, each of which makes an angle of 30.0° with the vertical. Draw a free-body diagram showing the various forces, and find...
  31. N

    B Vector of forces (question about how a scale works)

    so my question is a little dumb, if an object on a scale has a weight that points downwards and the scale exert normal force on the object upwards cancelling the forces acted on the object then what does the scale read? also the action-reaction pair to the normal force is supposed to be the...
  32. A

    Problem understanding the forces applied to a threaded fastner

    Greeting I have a problem understanding the forces applied to a threaded fastner I really don't understand from where they got Pr or PL because for me the only applied force is F thank you!
  33. TheBigDig

    Forces acting on a car on an incline

    For part 1, I got ## tan \alpha = 1/30 ## ##\alpha = 1.9^{\circ}## ##mgcos(1.9) = 10774N## I'm a little thrown off by the second part. Are we supposed to assume that in the absence of friction, F = N and then substitute F = ma to solve for this?
  34. J

    I Car acceleration if resistance forces don't exist

    Let imagine that car with constant 500HP accelerate but resistance forces don't exist (aero drag,internal friction in engine and transmision,tyer rolling resistance etc etc..) neglect fuel loss over time.. From 0-100km/h take in 4sec and burn 200mL petrol Will car accelerate from...
  35. G

    To find the forces on a composite object

    Could I please ask for help with the following: Here's a diagram: (in what follows, for clarity, I write L to represent the lower case L of the diagram). My diagram wrongly shows u (the coefficient of friction) to be the same at both points of contact. Since this image was taken I have...
  36. Z

    I Do Fictitious Forces Still Matter in General Relativity?

    hello it is well known that gravitationl force is actually a fictitious force generally speaking,are fictitious forces still necessary in general relativity ? the fictitious forces which we experience on a bus or on a car can also be understood as due to the spacetime distortion ?
  37. G

    To calculate the forces on a composite body

    Can I please ask for help regarding the following: A uniform rod AB of length 3L is freely hinged to level ground at A. The rod rests inclined at and angle of 30 degrees to the ground resting against a uniform solid cube of edge L. Contact between the rod and the cube is smooth and contact...
  38. curiousPep

    Confused about which forces are external when Newton's Second Law is used

    So I have a trolley of mass m that moves on a straight line. A sphere of mass m, is attached on the trolley with a light string of length a and it is left to oscillate. Just to give some idea of their positions: r_trolley = xi r_sphere = (x-asinθ)i - acosθj (θ is the angle between the string...
  39. H

    Calculating joint reaction forces

    I have this question in my biomechanics class, and the way the teacher has solved it raised some questions with me. This is the snippet of work from the lecture slides: But, if we see the red variables acting as 'placeholders' for the value of respective forces, and the value of the force at...
  40. S

    I Base Motion and Vertical Beam - Basic Reaction Forces?

    So I am trying to understand how to estimate the amount of deflection [D] the vertical beam shown above would experience if the base it is attached to is accelerating at a constant acceleration [a] of 9.81 m/s. I assume the Force [F] would be equal to weight of the vertical beam (mass x...
  41. ronald_hinh

    I Time Dilation: Gravitational & Velocity Effects Explained

    I'm trying to understand what the time dilation looks like when moving through space and then approaching a planet's gravity field. So I have the broad understanding that if you are moving near the speed of light in a spaceship, your clock ticks normal but the clocks on other stationary objects...
  42. K

    A Two equations of generalized forces

    Wikipedia article under generalized forces says Also we know that the generalized forces are defined as How can I derive the first equation from the second for a monogenic system ?
  43. K

    A Hamilton's principle and virtual work by constraint forces

    Found a question on another website, I have the exact same question. Please help me Goldstein says : I do not understand how (2.34) shows that the virtual work done by forces of constraint is zero. How does the fact that "the same Hamilton's principle holds for both holonomic and...
  44. S

    EMF due to Lorentz electric and magnetic forces

    Example of emf due to Lorentz magnetic force is motional emf. When rod PQ moves to the left, there will be downwards magnetic force acting on the positive charge in the rod PQ so point Q is at higher potential compared to point P so there will be potential difference (emf) between P and Q The...
  45. S

    B Question about the solar system and gravitational forces

    Alright, so I have a question. Now, on planets such as our Earth, there are a longitude and latitude as well as altitude. If I am not mistaken, I believe the latitude and altitude are part of what affects gravity, or weight, on a planet. Latitude makes it so that the object in question is...
  46. B

    B Why don't boxers' skulls shatter from the forces of punches?

    Hi All, My question is in relation to forces that can come through movement. For example, the skull is stated to take around 520 pounds of force or around 2000N: https://www.virginialeenlaw.com/help/how-much-force-can-a-human-skull-withstand.html However, boxers can punch well in excess of...
  47. Zeeshan Ahmad

    I Exploring the Oddities of the Four Fundamental Forces

    As we know that their are four fundamental force in nature Namely Electromagnetic force, strong and weak nuclear force and the gravity But we study regarding their properties And compare their properties we see a strange thing That for the case of strong nuclear force enspite of being the...
  48. C

    Calculate dimensions of floating laptop stand

    I am planning to build my own laptop stand with an acrylic sheet. The final product should look like the one in the attached image (bottom right) Material: most laptop stands are made with 6mm acrylic thickness, hence this is what I will use. Also I already have this material at home. I am...
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