Ball Definition and 999 Threads

BALL (pronounced "ball") is software consisting of the versatile C++ class framework Biochemical Algorithms Library (BALL), a set of algorithms and data structures for molecular modelling and computational structural bioinformatics, a Python interface to this library, and a graphical user interface to BALL, the molecule viewer BALLView.
BALL has evolved from a commercial product into free-of-charge open-source software licensed under the GNU Lesser General Public License (LGPL). BALLView is licensed under the GNU General Public License (GPL) license.
BALL and BALLView have been ported to the operating systems Linux, macOS, Solaris, and Windows.
The molecule viewer BALLView, also developed by the BALL project team, is a C++ application of BALL using Qt, and OpenGL with the real-time ray tracer RTFact as render back-ends. For both, BALLView offers three-dimensional and stereoscopic visualizing in several different modes, and applying directly the algorithms of the BALL library via its graphical user interface.
The BALL project is developed and maintained by groups at Saarland University, Mainz University, and University of Tübingen. Both the library and the viewer are heavily used for education and research. BALL packages have been made available in the Debian project in April 2010.

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  1. jmex

    Disc lifted by pressurized air in a vertical tube

    Hello, I have a circular pipe where there is an inbuild pressure and I have kept a circular weight on it. I would like to know what would be the lift of the weight under certain pressure. I know the relation that the minimum weight required to keep the pipe closed is F = P*A. (this F will be...
  2. yusungmagic

    Circular motion question: Mass on a rod rotating in a vertical circle

    By looking at the following question, I have no idea why the direction of force exerted by rod on a ball is represented like that. can anyone help me to understand?
  3. NikolasLund

    Friction force on a ball falling through a body of water

    I first attempted to solve the problem by ##A_{ext} = \Delta E_{mech} = F_{ext}s##. Here, ##F_{ext} = F_{friction}## and ##\Delta E_{mech} = E_{k2} + E_{p2} - E_{k1}##. We obtain then the following equation: $$F_{friction} = (m((v_2)^2 - (v_1)^2))/2h + mg,$$where ##v_1## is the velocity at time...
  4. SelzerRS

    Finding the intermediate height of a ball in terms of its maximum height

    Ive done this problem two different ways (sorry it’s messy) and keep getting hB = 1/9 hA, but my homework says it’s wrong. I’m guessing it’s because I assume that v0 is 0, but I’m not sure what other formulas or steps I need to take to either find or omit the variable. Are there any other...
  5. P

    Contact Mechanics: Deformation of a ball on a surface

    A solid ball of radius R, density ρ, and Young’s modulus Y rests on a hard table. Because of its weight, it deforms slightly, so that the area in contact with the table is a circle of radius r. Estimate r, assuming that it is much smaller than R. I have no issues understanding the...
  6. A

    B How to characterize a rubber ball moving horizontally and bouncing off of a vertical wall?

    So imagine we had a rubber ball and we threw it perpendicular to the surface of wall. The ball will obviously experience some “throwing” force — horizontal with respect to floor (let’s assume the ball is in perfect vacuum and there is no net torque). As it hits the wall, the normal force will...
  7. A

    Why does a plasma ball emit light?

    Is the cause of the lighting due to the impact of electrons with the nucleus
  8. graphking

    I A strict proof of "why the Earth is a ball"

    "bubbles are ball" is called isoperimetric problem in serious mathematic. In this topic, many essay were written. Here's my serious essay about "why earth ball", which has been rejected by arxiv and my mentors...... I would want to know if physicists are interest? I really think that is...
  9. J

    Revisiting the Feynman Ball on an Inclined Plane Problem

    Fw = sec(alpha) * kg-wt Fp = tan(alpha) * kg-wt
  10. M

    Impulse integration for a Tennis Racket hitting a Tennis Ball

    For this, Can someone please tell me why they integrate the impulse over from ##t_i## to ##t_f##? Why not from ##j_i## to ##j_f##? It seems strange integrating impulse with respect to time. Many thanks!
  11. S

    Medical 3 Ball Incentive Spirometer -- Exhalation mode?

    I have watched a few videos about how to use a 3 ball incentive spirometer for lung rehabilitation. Most of them are about inhalation, which you exercise with the device held right side up. I also saw a couple of videos where they hold the device upside down to test and strengthen exhalation...
  12. brochesspro

    The final velocity of a ball rolling while slipping.

    Here is the problem statement along with the figure. Here, I take the right-ward and anti-clockwise directions to be positive. After the ball collides with the wall, its angular velocity remains the same and its velocity changes direction while remaining the same in magnitude. Using the...
  13. J

    I Rolling ball, change of direction

    Say I have a magic way to exert lateral forces on a free-rolling ball on a plane, with no slipping. Say I apply a force for a given period from the South, the ball starts rolling to the North and attains a constant speed. Then I suddenly apply the same force for the same period but from the...
  14. paulimerci

    Find the magnitude of the momentum change of the ball?

    I understand that it is a 2D momentum problem with an elastic collision; Looking at the vector diagrams below, I notice that the velocity vectors initial and final in the y direction are in the same direction, indicating that momentum does not change, whereas the velocity vectors initial and...
  15. A

    I Distance traveled by a ball down a ramp and on a flat path

    Question: A ball is hit with a certain force and it starts with an initial velocity of V m/sec decelerating due to friction along a flat path and then up an inclined ramp coming to stop at the top of the ramp where the ramp becomes flat again (as per diagram A). The total distance traveled along...
  16. paulimerci

    Which statement is true? (Velocity and Acceleration of a Tennis Ball)

    I understand that when a tennis ball is in motion, the velocity vectors and acceleration vectors are pointing in the same direction. When the ball slows down, it is decelerating and comes to a stop. In the above statement, I understand that from the given angle, both vectors are pointing in the...
  17. graphking

    I In a 3-dimension isoperimetric problem, a ball maximizes the volume

    ...
  18. shivajikobardan

    JavaScript How to reflect the ball at an angle?

    Here's the full code: When a ball collides with bat or walls, I want the ball to be reflected with an angle, how do I do it? I suspect there's lots of physics to it. So, should I stop this project here? I'd have to probably build a part of game engine…Can anyone help here?
  19. Volt582

    Distance traveled by a Ball affected by friction after t seconds

    Hi everyone, i have been trying to find an answer to this problem I have but couldnt find any good answers... (I dont know much about this stuff, but need a formula for a Project I am currently working on). So The problem goes as follows: Assuming we have a ball with a mass of m which is...
  20. Rikudo

    Choose a ball at random from a randomly selected box - alternative way

    https://www.physicsforums.com/threads/choosing-a-ball-at-random-from-a-randomly-selected-box.1034377/ First of all, I would like to point out that this is the same exact question from what is being discussed in the thread above. In that thread, the problem is solved by adding the probability...
  21. String theory guy

    Average force when a bouncy ball collides with surface

    What have mistakes/wrong assumption have I made in solving this question? I tried to solve the problem this way N.B. I assume that the j hat direction is up.
  22. M

    Understanding Periodic Motion: Proving and Explaining its Repeating Nature

    For part (a) of this problem, The solution is, However why did say show the motion is periodic, but then the solutions don't show it, instead explain how it is periodic? Is there a way to prove that the motion is periodic other than the solution to part (b)? Many thanks!
  23. O

    How to Calculate the Bounces of a Bouncy Ball

    For school I'm trying to write some code to calculate the height of how high a ball would bounce given its mass, height, and the gravity of where it was dropped. I know there are more variables to consider, like wind resistance and the surface it was dropped on, but for now I'm trying to keep it...
  24. S

    Anyone notice that the World Cup ball is a Pyritohedron?

    The classic shape of a soccer (football for everyone outside of North America) is a Truncated Icosahedron. (And yes, all the shapes here are "rounded" forms. :rolleyes: ) https://fivethirtyeight.com/features/the-world-cups-new-high-tech-ball-will-change-soccer-forever/...
  25. C

    I Probability of White Ball in Box of 120 Balls: Solved!

    Problem: In a box there are ##120## balls with ## X ## of them being white and ## 120 - X ## being red for random variable ##X##. We know that ## E[ X] = 30 ##. We are taking out ## k ## balls randomly and with returning ( we return each ball we take out, so there is equal probability for each...
  26. susan_khan

    How to Calculate Speed of Head of Driver After Collision?

    A 0.045 kg golf ball is hit by a driver. The head of the driver has a mass of 0.15 kg, and travels at a speed of 56 m/s before the collision. The ball has a speed of 67 m/s as it leaves the clubface. What is the speed of the head of the driver immediately after the collision? I'm not sure...
  27. W

    Electronics Would This Setup for a Ball Bearing Accelerator Work?

    I need a method to accelerate a ball bearing down a pair of wire tracks, and to generate a consistent amount of force on every activation. Please critique my tentative design: I want to use an inductive coil activated by a proximity sensor to generate a transient EM field to accelerate the ball...
  28. M

    Finding COM of L-Shaped Rod and Ball System

    I suspect we can treat the L shaped rod as two rods and then find the com for that system and then find the com of the ball and that system
  29. E

    Relative velocity passing a ball between two soccer players

    For some reason I'm having trouble understanding relative velocity problems. I know how to solve this, but I keep guessing at random methods until my answer matches the solution in the textbook. I solved it correctly by breaking the velocity of the ball into x- and y- components, then solved...
  30. crememars

    Wind drag problem with a ball hanging on a rope

    I drew a FBD but I feel like it's wrong because there are too many missing values. I tried this: Fy = 0 Tcosθ - Fg = 0 Tcosθ = mg T = (1.2)(9.8) / cos(25) T = 12.98 N Fx = ma Fwind - Tsinθ - Fdrag = ma Fwind - (12.98)(sin25) - Fdrag = ma I don't know how to find these missing values. I feel...
  31. theanswer2physicsisu

    Air Resistance Question -- Dropping a tennis ball and a feather....

    I thought the one with more mass would fall faster
  32. SMOKEYWC

    Conservation of momentum (wrecking ball hits a stationary object)

    I have a wrecking ball with a mass of .5kg traveling at 3.03 m/s that hits a stationary block .9 meters high, weighing .06kg. I calculated the ball's exit velocity after it hits the block to be -3.00 m/s . I calculated the final velocity of th block to be 4.2 m/s Vf = Sqrt 2(g)(h) = sqrt...
  33. N

    Solving a Ball Thrown off a Cliff: How Long Does it Take?

    This is the question: A ball is thrown with a speed of 6m/s at an angle of 25° above the horizontal from the top of a cliff. The ball strikes the ground 15 m from the bottom of the cliff. How long does it take the ball to strike the ground? How long is the cliff?Here's a visual representation...
  34. Trikenstein

    I Ball free fall 100m at equator, where is the landing spot?

    We have a weekly fun random chat to break from the routine of WFH. A science quiz poped up. There is no consensus on the good answer. We need 3rd party opinion. You are at the equator, dropping a steel ball into a dry well, the depth is 100 meters, the mass of the ball is 1kg. The starting...
  35. P

    Time to reach Max. Height for a kicked soccer ball

    Vvertical=15sin30 = 7.5m/s d=Vvertical*t+0.5atsquared 0=(7.5m/s)t+0.5(-9.81m/s)t squared 0=t(7.5m/s-4.9t) t= 1.53s t=1.53/2 t= 0.76s to reach the maximum height Is this correct?
  36. A

    Pendulum made with a Ball and two light strings

    Sketch
  37. S

    Initial velocity and angle when a ball is kicked over a 3m fence

    Hello there, I don't understand what I'm doing wrong I don't get the correct answer, but have done the same analysis 3x already and still get the same... Some input would be appreciated thanks in advance. Note: y-axis is upwards and x-axis is to the right. 3 unkowns i.e. 3eqs. ##x = x_0 +...
  38. D

    B Question about collisions -- Knife point piercing a ball of clay

    I have a question regarding the collision of two objects, specifically something heavy falling on something with a point. For example, if a 50lb ball of clay fell from 10 meters onto the point of a knife, would the knife's point have to withstand the entire force of the clay before the blade...
  39. Tesla In Person

    Find the Height of a Building by dropping a ball from the top

    Hi, I have this kinematics question I am struggling with. There is a building from which a ball is dropped and it takes 5 second to reach the ground. Then they say that the same building is on a planet w/o atmosphere where g= 6 m/s^2 . What is the height of the building ? I approached this...
  40. C

    Transition matrix of a paint ball game

    Summary: Finding the transition matrix of a paint ball game where only 3 probabilities are given. We have the following question: Alice, Tom, and Chloe are competing in paint ball. Alice hits her target 40% of the time, Tom hits his target 25% of the time, and Chloe hits her target 30% of the...
  41. James Brown

    B Will a round-headed rod topple if it slides down a frictionless slope?

    Well, the problem is that, someone told me that a ball won't roll when sliding down a frictionless slope because the resultant force mgsinx is parallel to the slope which means that the ball will slide down the slope. Now, replace the ball with a round headed rod, does this means that the rod...
  42. Hurcane

    Answer the question about time of cooling of a ball

    Hello, I'm not sure if this is the right place to post my question, however I still want to know. Recently, my teacher asked me the following question: "In which of the cases will the cooling time be the least: 1. the ball is suspended from the ceiling 2.the ball lies on a stand with a thermal...
  43. G

    Projectile motion when kicking a ball that lands on an upward slope

    We know x = R =max range (28m) on level ground. Need to find v()^2. Subbing y=0 into (1) above, get v(0)^2 = (gR^2/)/(2*cos (theta)^2 * tan (theta). ... (2) This didn't seem right, since this means v(0)^2 is a negative number ... maybe my orientation or algebra wrong? Anyway, didn't see...
  44. U

    Golf Ball Projectile Motion Problem -- Solved

    26.6m/s = v0 36.5º = θ g = 9.81m/s^2 A) Find Range: (v0^2)/g *sin2θ = (26.6^2)/9.81 * sin2(36.5) = 89.99 I double-checked with the other Range equation (2v0*cosθ * (v0sinθ)/g) so I know I'm doing something wrong. Please help! Thank you edit: A) Correct answer is 69.0
  45. F

    Horizontal impulse on a ball at rest on a plane (with friction)

    Summary:: I'd like to check my understanding of standard problems where a billiard ball resting on a plane is hit horizontally at some height above its center So the situation is that a ball of mass ##m## and radius ##r## is at rest on a horizontal surface. There is friction between the ball...
  46. H

    Engineering Hydrostatic Pressure of Ball Floating in Liquid

    Let's say there's an object floating in liquid. The depth of the object below the surface is 𝑑 and its height above the water is ℎ. The density of the ball is 𝑝𝑏 and the density of the liquid is 𝑝𝐿. The pressure above the water is 𝑃𝑎𝑡𝑚. I understand this situation when only the density of the...
  47. J

    B How does the size of pool balls affect the amount of force needed for a shot?

    A=Cueball start position CP=Centre Point where balls collide B=The pocketHey guys, I was asked this question that seems completely obvious but I keep second guessing myself over it, I have included a basic picture to explain what I’m about to describe Say you were to take the above pool...
  48. G

    Momentum and Impulse Problem with a Ball bouncing off a Wall

    a) Assuming it is inelastic as it is accelerating and therefore kinetic energy is not conserved? Intuitively this doesn't feel right... b) change in momentum = p initial - p final = force x time p initial = 0 as at rest p final = 0.25 x v2 force x time = area under graph = 0.1 therefore 0.25 x...
  49. T

    Electrical Calibrating a metal leaf or pith ball electroscope

    I'm trying to build a DIY metal leaf or pith ball electroscope. I want to provide it with a circular arc voltage scale visible directly behind the (deflected) ends of the leaves. To calibrate the scale with ballpark accuracy, I want to determine the charge density upon the leaf pair (or pith...
  50. Eobardrush

    Ball rolling down a slope problem: Find an expression for time taken

    Question: Galileo released a metal ball from rest so that it could roll down a smooth inclined plane. The time t taken to roll a distance s was measured. He repeated the experiment, each time recording the time taken to travel a different fraction of the distance s. Write an expression for the...
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