What is Ball: Definition and 999 Discussions

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. R

    How does the kinetic energy of a swinging ball change with respect to height?

    Homework Statement Imagine a ball on a string that we swing vertically so that the hight changes. By conservation of energy the velocity of the ball must change right? Because at the highest point of the swing it will have maximum GPE but at the bottom, minimum right? Watching many videos has...
  2. B

    Forces on a plane exerted by a ball

    Could someone please provide a diagram of all the forces acting on the plane, and explain why the answer is E? This is from the 2014 F=MA exam. Thanks, blueblast
  3. J

    Two balls and a rod colliding with a ball

    Homework Statement Homework EquationsThe Attempt at a Solution The length of the rod is along y direction and (A+B+rod) is traveling along +x direction . Since there is no external force along x direction momentum is conserved along x direction . If v' is velocity of CM of (A+B+P) then 2mv...
  4. C

    Ball bounces several times on an inclined plane

    Homework Statement A ball falls on an inclined plane of inclination theta from a height h above the point of impact and makes a perfectly elastic collision. Where will it hit the plane again ? Solve the previous problem if the coefficient of restitution is e. Use theta = 45°, e = .75 and h =...
  5. Irfan Nafi

    Which ball has more energy halfway through the track?

    2 frictionless tracks have equal length bumps with one going up and the other down. Halfway through the track which one has more energy? Assuming that they started at the same height, I thought that they had the same amount of energy, but since Ball B ends up having a greater velocity at the...
  6. A

    A Ball is rolling on a flat surface

    Let's say we have a rolling without slipping (e.g. mentioned ball) on flat surface. Does it mean that the ball will accelerate to infinity ?
  7. B

    Ball in Rotating Disk: Kinetic Energy, Work, and Power

    Homework Statement A disk of radius ##R## has a cylindrical hollow that goes through it crossing its center ##O##. The disk rotates around its central axis with constant angular speed ##\vec{\omega}##. A little ball of mass ##m## and with the same radius of the hollow, is at a distance ##R_0##...
  8. W

    Ball thrown vertically, only the time is given

    Homework Statement :[/B] A ball player catches a ball 3.33 s after throwing it vertically upward. With what speed did he throw it? What height did it reach? Homework Equations :[/B] d = v0t + .5at2 I'm not sure whether this is one of the equations which should be used for this problem. [I also...
  9. S

    Ball Release and Thrown to reach ground at the same time

    Homework Statement A ball is thrown straight up from the edge of the roof of a building. A second ball is dropped from the roof 1.00s later. You may ignore air resistance. If the height of the building is 20m, what must the initial speed of the first ball be if both are to hit the ground at the...
  10. S

    Can Macroscopic Objects Tunnel Through Walls According to Quantum Mechanics?

    ok i read about that quantum mechanics article about how macroscopic objects have a extremely low probability of passing through a wall.Now i very clearly remember that 5-6 years back i have noticed my smiley sponge ball going into a place it cannot go to.Do you think it may have gone through...
  11. B

    Force exerted on counter-rotating wheels by a tennis ball

    Homework Statement I am trying to figure out what torque is applied to 2 wheels counter-rotating at 4,000 rpm when a tennis ball is squeezed between them and then propelled forward (because the wheels are counter-rotating).This is how a tennis ball machine propels a ball forward. I know the...
  12. M

    Why does a ball move in your hand when net forces are 0?

    This is a more general and probably silly question, but if you have a ball in your hand and you move it upwards, the acceleration will be positive then after you move it at constant velocity, acceleration will be 0. However, how is net force is 0 when the ball is still moving? You are clearly...
  13. E

    B Ball Lightning and Stars: Unveiling the Spectral Similarities

    Has the spectrum of a ball lightning ever been photographed? If so, does the spectrum look like the spectrum of any star? Could one say: the ball lightning is the smallest existing star?
  14. J

    Please confirm which solution -- Ball is thrown from a tower....

    Homework Statement Question is: Suppose a ball is thrown from a tower 70.0m high with an initial velocity of 3.00 m/s. What will it's speed be after 2.00s? Assume downward is the positive direction and neglect air resistance.Homework Equations I have a quiz on Monday in Physics and thought I...
  15. D

    Automated tennis ball launcher for my dog

    Hi all, I thought I would post my thoughts/progress on designing and building an automatic tennis ball launcher for my dog. The little fella gets a bit bored during the day when we are at work, so I want to build him this so he has something to do other than push a basketball around the...
  16. Pushoam

    Final speed of ball : collision with vertical plank at top

    Homework Statement Homework EquationsThe Attempt at a Solution I have solved the first part already. For the 2nd part, I am writing the relevant eqns. Can I take motion of the plank as a pure rotation about the pivot ? Quantities corresponding to pivot is subscripted by p. Conservation of...
  17. Pushoam

    Finding the speed of rolling ball

    Homework Statement Homework EquationsThe Attempt at a Solution In rolling motion, friction doesn't work. So, applying work energy theorem, ## \frac 1 2 m v_0 ^2 =\frac 1 2 mv^2 + \frac 1 2 I_{center} \omega ^2 ## ## taking~ I_{ center} = \frac 2 5 m R^2 ~and ~ v =\omega R , v = \sqrt {(...
  18. A

    Will a Ball Thrown in a Vacuum Move Forever Without Gravity?

    if I throw ball in vacuum and there is no gravity ,is the ball will be moving for ever or will move for just a time and stop? And thanks.
  19. T

    If a steel ball were to fall, how far away would it land

    Hello! Imagine you drop a steel ball of weight x from a variable height y. the ball hits a steel ramp on the ground which is at 45 degree's I would like to know how I could work out how far away the ball will land. I have had a good look around for this however the closest thing I can find...
  20. G

    Why does the ball need to be rotating before colliding with the surface to skid?

    An elastic spherical ball of mass m and radius a moving with velocity v strikes a rigid surface at an angle θ to the normal. Assuming the ball skids while in contact with the surface, the tangential reaction force being a constant fraction μ of the normal reaction force, and assuming the...
  21. Const@ntine

    Airgun shoots ball: Pressure = ?

    Homework Statement An airgun shoots a ball made from lead, through air of high pressure that pushes the ballforward like a piston. Because this happens very quickly, Q = 0 and the process is adiabatic. The initial volume of the air is Vi = 12.0 cm3 = 12.0 * 10-6 m3, which behaves as an ideal...
  22. F

    How Did This Guy Make a Soccer Ball Wobble On the Ground?

    Hello, Hello, I found this youtube video that I have been trying to figure out how they did for a while. Being the good men of science that you guys are, I figured you might be able to explain how he did this: I tried: Filling the ball with water(which worked at slower speeds) Over inflating...
  23. Spinnor

    Charged basketball, inertia ball and field

    I was wondering how much I would have to charge a basket ball of mass M, so that I would begin to feel the inertia of the electrostatic field energy. We can calculate the total electrostatic field energy surrounding the charged basket ball, call it E. Can we then equate this energy E with a mass...
  24. fluidistic

    Surviving a fire by going underwater in the bath with a ball

    I'm wondering whether it's possible to survive most fires by filling the bath with water and a balloon with air (it doesn't matter if it comes from human exhalation), then go underwater and breath through the balloon. When I was a kid I used to breath in a balloon that I would fill with air by...
  25. N

    Can a Metal Ball Levitate Using an Electromagnet?

    Hi guys, I am trying to produce a desktop feature for a client which consists of a 3d printed cube with a metal ball at its center. I can suspend the ball in the center of the cube using a support or piece of rod, but I would really like to try and make it levitate using an electromagnet. I...
  26. R

    One Ball fatigue failure at Deep Groove Ball bearing

    I am working on finding a solution for a gear box field failure. Failure description: In the deep groove ball bearing only one rolling element has a pre-mature fatigue failure (Image-6.jpg) and rest of the all ball is in good condition (image-05.jpg). Do anyone has seen the same kind of...
  27. T

    Calculating the Speed of a Ball Rolling Down a Hill

    So I know that given a unchanging hill, and same mass between a sphere and cube, that the cube should slide down the hill faster (assuming negligible friction). This is observed through the energy "lost" by the sphere which instead of having all of its potential energy transferred towards...
  28. Toreno

    Stargazing Lightning ball - me to analyze this rare video

    Hi, Some time ago I was looking for lightning ball videos on youtube. I observed some strange phenomenon recorded on one of the videos. Before a lightning ball is created, some "dark" ball is coming from above and then it immediately changes to the lightning ball which is moving at different...
  29. B

    Strange behaviour of roulette ball falling

    I have analysed some roulette spins with sony vegas in order to get the time for each turn of the ball. It is supposed that if the time that takes for the ball to complete a turn is higher, it means that its velocity is faster and thus the time at which it will fall off from the rim will be...
  30. deuce123

    Not sure if this approach is correct for ball falling past a window

    Homework Statement A ball is dropped from somewhere above a window that is 2.00 m in height. As it falls, it is visible to a person looking through the window for 200 ms as it passes by the 2.00 m height of the window. From what height above the top of the window was the ball dropped? Is...
  31. Victoria_235

    Circular wire with ball and spring problem

    Homework Statement Here is the problem. A small ball of mass m moves without friction attached to a cwire. The ball moves under the action of gravity and a spring of constant k whose other end is fixed in the point A, with OA = R / 2. The spring is tension free when the spring is R/2 to...
  32. ih8pa1n

    Momentum of ball on a pool table

    Homework Statement Picture looks like this: ----------------------- ○ (empty space) ● (Cue) (White ball) (Black Ball) Mass: Cue (595g), White Ball (170g), Black Ball (155g) Question: On the given pool table, the white ball bounces off of the black ball and moves in the direction...
  33. N

    Newbie question -- A train in space with a ball floating in a train car....

    Hello, I am someone who has no experience in physics other than primary/high school and I have a quick simple question about something I can't wrap my mind around as a complete physics newbie. Please have understanding. The question: let's say a train is standing still at a point in space (so...
  34. Alexander350

    Why is it quieter to lower your hand when you catch a falling ball?

    If there is a ball falling from a height due to gravity, and you keep your hand still and let the ball fall onto it, it stops suddenly and makes a loud noise. However, if you lower your hand as you catch the ball, like when a cricketer catches a fast moving ball, the catch is almost silent. I...
  35. Faefnir

    How High Will the Ball Bounce on an Inclined Plane?

    A ball, which can be regarded as pointin all its effects, falls steady , subject only to the weight force, on an inclined plane of an angle α with respect to the horizontal from a height h computed from the impact point. The ball bounces elastically. Get the d height can reach the ball and the...
  36. M

    MHB Calculating Ball Height and Time with Quadratic Formula

    A ball is thrown straight upward. Suppose that the height of the ball at time t is h = -16t^2 + 96t, where h is in feet and t is in seconds, with t = 0 corresponding to the instant the ball is first tossed. A. How long does it take for the ball to land? To do A, I must let h = 0 and solve for...
  37. sunnyday

    A ball is dropped from the top of a 55.0 m high cliff

    Homework Statement A ball is dropped from the top of a 55.0 m -high cliff. At the same time, a carefully aimed stone is thrown straight up from the bottom of the cliff with a speed of 21.0 m/s . The stone and ball collide part way up. How far above the base of the cliff does this happen...
  38. A

    How high did my golf ball go? (I have time of flight straight up)

    Years ago, I made a golf ball launcher. It shot straight up at a 90 degree angle. From launch to landing only 2 feet from where it started, it took about 20 seconds before it was back on the ground. Is there a way to determine its maximum speed and height it reached? This has been bugging me for...
  39. J

    Ball bouncing on a planet (no atmosphere) follow up questions

    This thread will contain several follow up questions, but let me start with the most simple one. Imagine a planet with no atmosphere and a ball in empty space. The ball is dropped on the planet from a certain height and starts bouncing. We ignore friction and consider this to be the fully...
  40. S

    Numerical integration in Python (throwing a ball)

    Homework Statement I have a problem with my physics task, but you do not need to understand physics to be able to help me, because my main problem is bad programming skill. I am dealing with a problem of throwing a ball in the air at an angle between 0 an 45 degrees. I need to consider not only...
  41. parshyaa

    What will happen if i throw a cricket ball through Saturn's ring

    Suppose i hit a ball with a speed around 177km/hr(when it is near Saturn's ring), will it cross the saturn's ring or it will move around saturn just like other dust partices, what will happen if the speed is around 344 kmph(speed of sound).
  42. davenn

    Cool ball and feather drop experiment

    some may not have seen this video done in a vacuum chamber enjoy
  43. C

    One ball dropped, another ball launched

    Homework Statement A ball is dropped from rest at height ##h_0## above the ground. At the same instant, a second ball is launched with speed ##v_0## straight up from the ground, at a point directly below where the other ball is dropped. (a) Find a condition on ##v_0## such that the two balls...
  44. Z

    Veocity time graph for a tennis ball during a rally?

    Hi all, I am trying to draw a velocity time graph for a tennis ball during a rally. I am aware that the horizontal component of the velocity/speed will be constant, assuming negligable air resistance, and that the vertical component of the velocity will be a sawtooth shape. However I am unsure...
  45. D

    Calculate angular velocity of a ball rolling down incline?

    Homework Statement An 7.80-cm-diameter, 400 g solid sphere is released from rest at the top of a 1.70-m-long, 20.0 degree incline. It rolls, without slipping, to the bottom Homework Equations I=2/5 Mr^2 K = 1/2 m*v^2 Kroll = 1/2 Iw2 mgh=K+Kroll The Attempt at a Solution Using the above energy...
  46. R

    Wrecking ball torque question

    Homework Statement At one point during its swing, a wrecking ball exerts a tension force of 9800 N on its cable, which makes an angle of 30 degrees with the horizontal. The crane's 9 m long boom is at an angle of 55 degrees with the horizontal. What is the torque exerted by the wrecking ball on...
  47. M

    Fluids and Ping Pong Ball Magnus and Coanda Effect

    Hi PF! Given a hairdryer blowing vertically against gravity toward a ping pong ball the ping pong ball is suspended. The ball is relatively stable in the jet because the high velocity of the jet causes a decrease in pressure, causing the ambient air to mix, therefore keeping the ball in the jet...
  48. physicaled

    Circular Motion: Ball on String

    Homework Statement A 1.5 kg ball is tied to a string that is .75 m long and whirled in a verticle circle. A) Find the tension in the string at the top of the circle B) Find the tension in the string at the bottom of the circle Homework Equations Fc=mac ac= v2/r The Attempt at a Solution A)...
  49. P

    Bowling Ball rolling on a smooth floor

    Hi there! I chanced upon this problem whilst trying to brush up my Classical Mech knowledge and found it confusing. Hope someone out there can provide an insight! Homework Statement A bowling ball of mass m and radius R sits on the smooth floor of a subway car. If the car has a horizontal...
  50. D

    Thermodynamics of a cannon ball / musket ball shot bullet

    I am a computer scientist currently writing a 3D simulation for high speed projectiles both sub and supersonic for various shapes and sizes of projectiles. For now I am focused on completing simulation of a simple model of a round ball shaped projectile (ie a cannonball or musket shot). I like...
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