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. A

    Angular momentum of a falling ball

    (L) = (radius) * (mass*velocity) velocity= 0+ (9.8m/s^2) (0.7s) = 6.86m/s (L) = (0.77m) * (2kg*6.86m/s)= 1.05 kg*m^2/s angular momentum points towards Polly
  2. H

    How Do Kinematics Apply to a Fielder Catching a Ball?

    I don't know how to approach this question. This question is on my Midterm tomorrow and the teacher gave it to us without the values in order for us to get an understanding help
  3. D

    Throwing a ball out of the end of a moving train

    Let's say there is a train moving at 50 mph on the moon on a flat surface (say it's a perfect vacuum) and you are on the last cart where you throw a ball out the rear in the opposite direction the train is moving (directly away from it, parallel to the ground). The ball thrown is also...
  4. P

    Describe the physics of a golf ball flight off the club face

    How did you find PF?: social media The flight of a golf ball off the club face at the moment of strike would seem to be determined, among other variables such as elasticity, by the mass of the ball, the club's force vector, and the orientation of the club face relative to that force vector...
  5. jisbon

    Rate of change (ice ball melting)

    So to begin this question, I do know that volume =4/3 pi r cubed, while the surface area) 4 pi r squared. I will like to clarify some things about the question: 1) does the first sentence means dv/dt is proportional to 4 pi r squared? 2) given the second sentence how am I able to construct an...
  6. Addez123

    Smooth rolling ball rolls down hill, how far can it fly?

    Figure of the problem. There are many exercises like these, and I've read the whole chapter and I got no clue where to start here. Kinetic energy from gravity is: E = mgh = 39.3m I could try change v to ωr in the K equation but it will leave me nowhere because I don't have the mass nor the...
  7. M

    Α baseball player throws the ball....

    Hi all ! I wonder if I'm right. (From : Fundamental University Physics, Volume 1 (Mechanics) - (Marcelo Alonso, Edward J.finn) Addison Wesley 1967) This is my try: * I have the Greek version of the book and there is no answer.Thanks.
  8. F

    Need Advice: Passing a Ball Bearing from Air to Water

    Hi all, I'm new to this but joined in the hope someone with more experience could provide some advice. In a personal project, I have a particular design dilemma where I am trying to pass a metal ball bearing (or any other spherical shaped solid) from a column of air into a column of water...
  9. B

    Finding the Acceleration of Gravity from these Dropped Ball Experiments

    Did not know where to start so I tried A= v/t to find velocity then plug into equation to find g, but i got a huge g.
  10. Jregan

    A golf ball being hit on the moon vs Earth

    I am just not sure if I did this properly. My professor hasn't really gone over when to use the range equation but I would assume range would equal the distance traveled therefore can be used for this problem. If not the how would I go about solving this? I did 1/6*9.8=1.63 for g on the moon...
  11. dilby

    Principles behind a ball pitching machine

    Hi all - I'm not an engineer or even very good at physics, but I was hoping to learn about something I'm interested in. I bought a ball pitching machine that I've outgrown and I'm wondering about either modifying it or even building my own and wanted to know about some of the key principles...
  12. Boyi

    What factors affect a golf ball's drag and lift besides spin and speed?

    Summary: What could affect Magnus force's magnitude and direction except for speed and spin? Most golf flight simulators model the coefficient for drag (Cd) and lift (Cl) as a function of the relative spin ratio (rsr), where rsr = spin * radius / speed. In Figure 1, parameters of two similar...
  13. vxiaoyu18

    How to calculate this torque? (steel ball in a spiral tube)

    Want to let the steel ball move upwards at a uniform speed, how is the torque of the spiral tube calculated? The parameters can be assumed by themselves. **The spiral tube is fixed on the central shaft, the central shaft is mounted in the ball bearing, and the thrust F acts perpendicularly on...
  14. S

    Tension and speed of bowling ball pendulum passing the equilibrium position

    For part a I used conservation of energy. -m*g*cos(θ)*L+1/2*m*0^2=-m*g*L +1/2*m*v^2 => v = sqrt(2*g*L(1-cos(θ )). b) For b I was think that T = mg in the equilibrium point but that doesn't invole θ in the answer. So that's why I tought that T*cos(θ ) = mg. So that the tension is mg/cos(θ). But...
  15. jisbon

    Relative velocity of a ball thrown inside a moving truck

    Hi all, Not sure on how to start this question in the first place, but from what I gathered from the data given I managed to derive this from the question: ##\theta = 53.13\deg## Let inside truck be t, final position be f, and ground be g ##D_{ft} = L## ##D_{fg} = xL## Also, for velocity...
  16. Wrichik Basu

    Perfect Floating Ball Illusion (inspired by Jeff Koons' Art)

    Recently I chanced upon a video from the Royal Institution. The host has tried to replicate a piece of art by Jeff Koons (snapshot from video): At Ri, they have tried to produce the same thing by balancing the ball filled with water, in a tank containing saturated saline water at the bottom...
  17. UnPetitGarcon

    Direction of a rope with a ball inside an accelerating box

    A steel washer is suspended inside an empty shipping crate from a light string attached to the top of the crate. The crate slides down a long ramp that is inclined at an angle of 37° above the horizontal. The crate has mass 180 kg. You are sitting inside the crate(with a flashlight); your mass...
  18. I

    Can a Fish Move a Ball in Water?

    if you put a fish in a plastic ball filled with water, can the fish make the ball roll by swimming. just like my hamster can make the ball roll by walking. thanx.
  19. brotherbobby

    STATICS – Pushing a ball over a curb

    I am able to solve the problem for both cases (a) and (b) using ##\Sigma \tau = 0##. It is only when, stranglely, that I use ##\Sigma F=0## for the ball that I run into trouble. Let me provide the solutions. (a) Using ##\Sigma \vec \tau = 0## about the tipping point, ##mg R\cos\theta = F_C R...
  20. PeterDonis

    I Gravitational Mass of a Ball of Photons: Concept Q10.4 in Gen Relativity

    This is based on "Concept Question 10.4" in Andrew Hamilton's General Relativity, Black Holes, and Cosmology. I have modified the question somewhat in order to focus on what seem to me to be the key issues. Suppose we have a spherically symmetric ball of stress-energy surrounded by vacuum. More...
  21. DharshanT

    Finding the magnification of a ball lens

    I don't really know how to relate the effective and back focal lengths for magnification purposes. Literature review suggests that a lens of 1mm diameter can have a magnification of 350x-400x, but I don't really know the calculations behind it. Please advise.
  22. A

    Why friction plays no role in this non-slipping billiard ball problem?

    =================== Now, I can get the solution in the book by writing and solving the force and the torque equations together with the non-slipping relation between the angular acceleration and the center of mass acceleration. However, the book solution only arises if there no friction between...
  23. M

    Mathematical description of a ball hitting a glass plate and causing damage

    Summary: damage on glasses plate by hitting ball If a ball hit a rectangular plate of glass and it cause a damage "but it didn't broken" how can i represent this damage using mathematics? I'll tell you my idea about it: let the ball move horizontally and hit the plate perpendicularly with...
  24. T

    Bounce of the cue ball in snooker

    I was watching a game of snooker, and sometimes the cue ball bounces off the cushions with surprisingly high speed. Some people often say that it comes off the cushion faster than it went into it. And I started thinking - is that even possible? Does physics work that way?
  25. M

    Ball Lightning Discussions/Anecdotes?

    New to the forums. Hoping to find a thread, forum, website dedicated to the discussion of/gathering of anecdotal reports of ball lightning. My mother's best friend witnessed what we believe is ball lightning in her home yesterday. She didn't get photos or video, but took some photos of odd...
  26. T

    Plasma ball radio-frequency energy

    I read Wikipedia's description of how a plasma ball works. Question: What kind of energy is the "radio-frequency energy from the transformer"? Is in the form of electric field energy, magnetic field energy, or both? Thank you! (from Wikipedia)... Although many variations exist, a plasma lamp is...
  27. H

    I Measuring Mass of a Bowling Ball Dropped into a Black Hole

    In a recent thread we discussed the idea that an object slowly dropped into a black hole, can have its rest mass recovered, as energy, if slowly brought to a halt at the event horizon. Once the object is dropped, it would be unrecoverable, and the BH would gain no new mass. I am under the...
  28. M

    Calculate the tension in a rope attached to a ball in circular motion

    The solution to the problem simply states: "Use of mv^2/r = 2000. T = (2000 + 7500) = 9500N". I don't understand this solution. Nothing more is provided. I don't know how you are supposed to find the radius (in order to use the centripetal force formula) merely from the information provided...
  29. V

    Class Project: Marble Ball Launcher [Help]

    What I'm here to find out: I am in the early stages of a physics project to build a electric circuit or use an electrical source to power the force that will carry a marble throughout the mechanical portion of the project, going through linear acceleration and circular motion. I'm not sure what...
  30. B

    Closed form of the position of a bouncing ball

    I know that the height before the first bounce will be ##y = g * t * t + v_0 * t + y_0##. After the first bounce, I can find y by pretending the ball was thrown from the ground with velocity ##e * -v_f## with ##v_f## being the velocity of the ball when hitting the ground, but I have to reset the...
  31. ejantz

    A billiard ball moves at a speed of 4.00 m/s and collides elastically....

    I know this question has been asked before but I really need some help finishing this final piece of the puzzle.. I have attached an image of my work to show how far I have gotten towards the solution but my unfamiliarity with trigonometry equations has gotten my stuck. Please assist! thank you
  32. pairofstrings

    B What is in a Jumping Ball?

    I am a beginner and I know a little bit of Math. Can anyone tell me what concepts in Math do I need to know to see one ball jumping in space? I need names of the concepts which let's me realize this Jumping Ball. Thanks.
  33. S

    Find the velocity of the ball

    Hi all! I was attempting the following question but my answer differed from the given answer. Please help me to solve it. Thanks. My answer = 2.45 m/s Given answer = 3 m/s
  34. A

    Tennis Ball Launcher: Build a Mechanical Launcher

    I have a project which consists in making a tennis ball launcher for training kids (6-12 years), but there is a catch, the mechanism can't have any elastic parts (springs, bands, rubber). It has to be purely mechanical. I need help
  35. Curtiss Oakley

    Bowling Ball Changing Rotational Direction

    I already have a and b, but want to see if anyone is willing to verify my answer for part c. I get 0 for the frictional force between the ground and ball, which would lead d and e to be 0 as well. Physics is rarely that easy so I wanted to make sure I didn’t miss anything.
  36. M

    Throwing a ball horizontally on the moon and pushing it in the spacestation

    Why is there a difference in force required throwing a ball horizontally on the moon and pushing it horizontally it in the spacestation Thanks
  37. jaewonjung

    Calculations for a ball tossed vertically upward

    I tried to substitute 1/2T in for T, because 1/2 T is when the ball is at H. With that, I found Vo, which was (H-1/8gT^2)/(1/2T). I plugged in Vo into h=vot+1/2gt^2 and put 1/4 T for t, but I could not get an answer in terms of H
  38. Khatti

    Gravity in a Swiss Cheese ball

    I'm working on a planet that is earth-sized, but has been essentially a dead stone for millions of years: no volcanic activity, the core has completely cooled down, the atmosphere has long since drifted off. In turn it has been mined for so long that a sixth of its mass has been dug up and...
  39. P

    Is Ball Bouncing on a Surface a Simple Harmonic Motion?

    Answer is C.
  40. M

    A Why does the characteristic function not converge in the L1 space?

    Hi PF! When proving a closed ball in ##L_1[0,1]## is not compact, I came across a proof, which states it is enough to prove that the space is not sequentially compact. Counter example: consider the sequence of functions ##g_n:x \mapsto x^n##. The sequence is bounded as for all ##n\in \mathbb N...
  41. osten

    Oscillation Problem -- Ball mass on the end of a horizontal spring

    Homework Statement A 200 g ball attached to a spring with spring constant 2.40 N/m oscillates horizontally on a frictionless table. Its velocity is 20.0 cm/s when x=−5.00cm. What is the amplitude of oscillation? Homework Equations f=√(k/m) /2π x(t) = Acos(2πft) v(t) = -2πfAsin(2πft) The...
  42. C

    Projectile Question -- Kicking a soccer ball through two holes in two walls....

    Homework Statement Find the initial velocity for the above soccer kick. Note that ball must cross the 2 points in the diagram within the two walls. Linked below is the diagram Homework Equations dx = v1(cos theta) * t dy = v1(sin theta) * t - 0.5at^2 The Attempt at a Solution I tried using...
  43. Np14

    Impulse applied to a bouncing ball

    Homework Statement A 0.500 kg ball is dropped from rest at a point 1.20 m above the floor. The ball rebounds straight upward to a height of 0.700 m. What are the magnitude and direction of the impulse of the net force applied to the ball during the collision with the floor? Homework...
  44. C

    What force keeps the ball levitated?

    What is reason that ball do not falls down,curved water jet low pressure because of centrifugal force or? How water jet transfer force to the ball,through pressure? As I know fluid can only moves object through pressure...
  45. TheQuestionGuy14

    Conservation of Energy and a billiard ball

    The conservation of energy states energy can never be created nor destroyed, and the amount of energy in a system is always constant. I'm just curious, say if a billiard ball just suddenly started moving without any other object making it do so, (kinetic energy was created), if it also suddenly...
  46. I

    Snell's law problem about a hemispherical glass ball

    Homework Statement I have posted the snapshot of the problem. Homework Equations Snell's law equations The Attempt at a Solution Now the problem says that laser travels through air vertically upward to reach the outer surface of the glass half-cylinder. If that is the case, then from Snell's...
  47. ju456one

    Projectile Motion: Pitcher throwing a ball to a catcher

    Homework Statement determine the acute angle (in radians) of appropriate elevation in the throwing of a ball, if the initial velocity is 20 m / s, g=9.81 m/s^2 and the distance in x is 40m. The ball leaves the hand of the pitcher with an elevation equal to 1.8m and the catcher receives it at...
  48. S

    Exploring Conservation of Energy: Ball Dropped in Water

    My question: Consider an isolated system consisted of a ball, and a bucket of water. The ball is released from height, H above a bucket of water. The initial temperature of the water-bucket system and the ball are T1 and T2 respectively. What will be the final temperature of the water after the...
  49. B

    Angular and Linear Momentum Problem

    Homework Statement A system has a ball and a uniform rod. The rod is rotating about point X on a frictionless table until it strikes the ball. The rod stops and the ball moves away. Variables: Rod's mass: m1 Ball's mass: m2 Rod's original angular velocity: ω Ball's final velocity: v Rod's...
  50. C

    Hard Kinematics problem: Ball thrown into the air

    Homework Statement A person throws a ball up from a height of 1.5 meters, 3.23 seconds later, the ball hits the ground next to you. Find the maximum height the ball reaches. Homework Equations V=V(initial)+at The Attempt at a Solution This problem almost seems impossible without knowing what...
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