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. Philosophaie

    Double Integral Surface Area of Spherical Ball

    Homework Statement Double Integral Surface Area of Spherical Ball radius Homework Equations ##\int_S d\vec{S} = 4*\pi*a^2## The Attempt at a Solution ##\int\int_0^a f(r,?) dr d? = 4*\pi*a^2##
  2. Philosophaie

    Spherical Ball with uniform Charge Density

    I want to find ##\Phi## and ##\vec{E}## for the general case of a Spherical Ball with uniform Charge Density centered at the origin radius d. ##\Phi = \frac{\rho}{4*\pi*\epsilon_0}\int\int\int\frac{r^2*sin\theta}{|r-r'|}dr d\theta d\phi## ##E =...
  3. Philosophaie

    Electrical Field around Spherical Ball at origin

    Homework Statement Spherical Ball centered at origin uniform ##\rho## with a radius a. Find E along x-axis. Homework Equations ##E = \frac{\rho}{4\pi\epsilon_0}\int\int\int\frac{r^2*sin\theta}{r_\rho^2} d\phi d\theta dr## The Attempt at a Solution Evaluate E spherically along the...
  4. N

    Angular Momentum of a paint ball

    Homework Statement A paint ball fires a ball of putty at a pendulum at a speed of 14 m/s, with a mass of 53g, at an angle of 42 degrees below the horizontal. The pendulum is made of a thin bar 51 cm long and mass of 310 g. The sphere fixed to the end of the pendulum is 17 cm in radius and has...
  5. L

    Scaling Maxwell's Demon Experiment: Macro-Level Rigid Ball Suspension

    I had the concept of scaling up Maxwells' demon experiment to a marco scale. Replacing molecules of gas with light, rigid, balls. Perhaps coated in magnets with varying poles so they never touch (non-interacting). Would suspend them in a thin fluid with neutral buoyancy.
  6. F

    Can a ball roll fast enough that it becomes airbourne while rolling?

    For ex, say you were rolling a ball down a steep ramp (about 85-90 degrees to horizontal, so almost straight). The ramp is say at least 100m long so there's enough time for the ball to build up velocity, etc. Is it possible for any circumstances to happen where the ball would temporarily...
  7. S

    Circular motion of ball and string question

    Lets say we have a ball on a string and we spin it around. The ball will undergo circular motion. The tension in the string is what provides the centripetal force, directed inwards. Then what would be the force directed outwards? (According to Newton's third law of motion). It can't be...
  8. P

    Ball hitting a wall at an angle - x and y motion

    Hello! Hopefully this will be a fairly straightforward conceptual problem. A heads up - while this problem clearly deals with momentum and elastic collisions, we haven't actually covered these concepts in class yet. I'm getting the idea, but am still a bit hazy here and there. Homework...
  9. M

    Centripetal Force and ball of string

    Hello, could someone look over my answer? I am not very confident I did the problem correctly. Homework Statement A 76-kg ball is tied to one end of a massless string of length The other end of the string is tied to a nail in the center of a table. The ball is set into uniform circular...
  10. M

    Bowling ball goes from sliding to rolling

    Homework Statement A bowling ball is thrown down the alley with speed ##v_0##. Initially it slides without rolling, but due to friction it begins to roll. Show that its speed when it rolls without sliding is ##\frac{5}{7} v_0##. Homework Equations ##K= \frac{1}{2}mv^2 + \frac{1}{2} I...
  11. 1

    When a ball hits the ground, where in the ball is potential energy = 0

    This is a question that me and a friend have been wondering. He says that when the ball hits the ground and is at rest for a very brief moment, potential energy will be 0 in the center of the ball, while I thought that it doesn't matter as the entire ball's potential energy is at 0. Which answer...
  12. N

    Center of mass with 2 people, a medicine ball, and a beam

    Homework Statement A person with mass m1 = 50 kg stands at the left end of a uniform beam with mass m2 = 95 kg and a length L = 2.4 m. Another person with mass m3 = 60 kg stands on the far right end of the beam and holds a medicine ball with mass m4 = 14 kg (assume that the medicine ball is at...
  13. C

    Projectiles - person kicks a soccer ball at an angle

    Projectiles -- person kicks a soccer ball at an angle Homework Statement a) A person kicks a soccer ball at an angle and sends it in the air. What angle of projection between 0 and 90 degrees produces the greatest initial vertical component? Greatest intital horizontal component...
  14. D

    What is the work of a moving bowling ball?

    Homework Statement A bowling ball of 7.21kg is thrown, it has an initial velocity of 12.5m, if his mouvement happens over 1.24m, what is the work of the bowling ball. Homework Equations W = FΔd W = F (Cos∅)Δd The Attempt at a Solution I think this is a trick question, but I'm...
  15. B

    Resistance - fluid resistance to ball motion

    Resistance -- fluid resistance to ball motion A ball of mass m = 3 kg is falling from an initial height y = 3 m in an area where the acceleration due to gravity can be approximated as g = 10 m/s2. As it falls the ball is subjected to a fluid resistance of magnitude FR = kv where k = 6 kg/s. How...
  16. N

    Can Blood Balls Cool Faster in Vacuum or Air?

    Hi, If we took the blood of all people here on Earth and made a ball of it (r=200, T = 310 K) how long would it take for it to cool down to ~ 285 K in vacuum (absent of sunglight)? How long would it take to cool down in air, with reasonable conduction speeds?
  17. H

    Reversibility of evaporating ice ball

    Homework Statement A ball of ice is thrown against a wall with such as speed than the ball of ice evaporates. Is this process reversible? Homework Equations if entropy doesn't change, process is reversible. The Attempt at a Solution I'm pretty darn sure the answer is no, but I am...
  18. U

    For a ball falling through a fluid, does the ball do work on the fluid

    So when a ball falls through a fluid in which it is submerged, it keeps displacing fluid as it descends, but the level of the fluid doesn't rise. So does the ball do work on the fluid? (Assuming there is no viscosity, the K.E would keep increasing, while potential energy decreases...that's...
  19. A

    Magnetic confinement of plasma ball

    I was taught (In my old thread which was then closed by a mentor) that it is impossible to magnetically confine a plasma ball. But I've since then had an idea how it could be possible: Instead of using a steady magnetic field, use a rapidly rotating magnetic field. The field lines are always...
  20. C

    Collision of ball with inclined plane problem

    Hi friends, I have an issue in solving a Collision of ball with inclined plane. Please Help me in solving this. Thank you all in advance. The problem is as: https://fbcdn-sphotos-a-a.akamaihd.net/hphotos-ak-frc3/q71/s720x720/1379765_1432382863655486_1628611844_n.jpg Attempt...
  21. J

    Ball swinging from a rope - Net force and curved path

    Help Please -- Ball swinging from a rope Homework Statement A ball of mass 30 kg is hanging from a rope of 3 meter tied to the roof of a truck. The truck is moving at a constant speed of 29.6 m/s. As you look forward at the ball hanging from the roof of the truck, you see the ball hanging...
  22. FOIWATER

    How the electric field inside a charged ball is zero

    I am having issues with multiple gauss' law problems. Assume we have a charged spherical surface. Inside the surface, E=0V/m. But why? I understand that at the center it should be zero due to symmetry, but why would it be zero at some point say, inside the surface but not at the center...
  23. C

    Any way to predict when to stop a moving ball in order to get it to x?

    I am working on a project for my kid. I have a question. Question: Is there a way to predict when to stop a moving ball in order for it to finally stop rolling at a specific position? Data: I know the balls x and y position, and the velocityX and velocityY float values. I think it has an...
  24. M

    Proving an open ball is connected in a metric space X

    Homework Statement . Let ##B(a,ε) (ε>0)## in a metric space ##(X,d)##. Decide whether this subset of ##(X,d)## is connected or not. The attempt at a solution. Well, I know open intervals in the real line are connected. I suppose that an open ball in a given metric space can be imagined...
  25. A

    A Rolling Bat Struck by a Ball

    A bat lies along the x-axis so that the tip of its handle is located in (0, 0) while the other end is at (0.9 m; 0). The center of mass is at (0.6 m; 0). A ball hits the bat perpendicularly at (x, 0), causing an impulse I. The bat’s moment of inertia through the center of mass is J = 0.0530...
  26. S

    Newton's Third Law of Motion and wrecking ball

    "For every action there is an equal and opposite reaction." I'm having a difficult time wrapping my head around this. I'm having a hard time applying it to certain situations. For example, a hammer hitting a nail, but more presently a problem in my homework. A building is being torn down...
  27. A

    Physics Energy - how fast ball is moving from certain height

    Homework Statement You let a ball roll from rest from the top of a ramp sitting on a table. If the top of the ramp is 12 cm above the top of the table, how fast is it moving when it reaches the bottom? Use g=9.8m/s/s Homework Equations Convert 12 cm to meters an you get .12. Then...
  28. P

    How Does Throwing a Ball from a Moving Flatcar Affect Its Trajectory?

    Homework Statement A person is riding on a flatcar traveling at a constant speed v1= 20 m/s with respect to the ground. He wishes to throw a ball through a stationary hoop in such a manner that the ball will move horizontally as it passes through the hoop. The hoop is at a height h=4 m above...
  29. D

    Projectile Motion ball throw help

    Homework Statement A ball is thrown off of a 15m cliff at an angle of 30 degrees above the horizontal and strike the ground 10.4 seconds later. Determine the initial velocity of the ball, the maximum height of the ball, and impact (final) velocity of the ball. Homework Equations vo=vf+at...
  30. B

    Soccer ball rebouncing of the goal post

    Homework Statement A 420 g soccer ball traveling at 23 m/s hits the goal post and rebounds at 18 m/s. If the ball is in contact with the post for 3.3 ms, what is the average acceleration of the ball during this time interval? Homework Equations Here I used 23m/s as initial velocity v_i and...
  31. L

    Imaging the surface of a half ball lens

    Hi, I'm new to this forum and I have an application where I want to image an object that is in contact with the round side of a half ball lens. I've attached a brief project description. I think this topic on optics is suitable for the Differential Geometry forum, but please let me know if...
  32. G

    Possible forces acting on the ball rolling down a slope?

    neglecting friction from the slope and air resistance, what are the possible forces acting on the ball? i can only think of 2: gravitational force by the Earth on the ball. normal force exerted by the slope on the ball. are there any other forces else that i missed out?
  33. K

    Projectile motion, throwing a ball at a coconut

    Homework Statement You throw a ball at a coconut on a stand 4.0 m in front of you and 1.0 m above the point at which you release the ball. If you throw the ball at 10.0 m/s, at what angle(s) should you throw it? How long is the ball in the air in each case?Homework Equations ##v=v_o + at \\...
  34. E

    Rolling a ball down an inclined slope. Something's wrong.

    Hi guys, Homework Statement I'm trying to find the theoretical time it takes for a glue stick to roll down an inclined plane of 10 degrees. We then have to compare it to the practical value, which was 1.09 secs.(Average over 10 repetitions). The glue stick has a mass of 10g. The distance of...
  35. M

    Ball Trajectory: Solve for x(t) & y(t) & y(x)

    Homework Statement A cannon shoots a ball at an angle \theta above the horizontal ground a) Neglecting air resistence, find the ball's position (x(t) and y(t)) as a function of time. b) Take the above answer and find an equation for the ball's trajectory y(x).Homework Equations...
  36. L

    Help Motion of a Ball Physics Homework

    I have this question for my physics homework and I really don't understand it please help me! It's probably a really simple question but I just can't get my head round it! 1. a) at what time does the ball reach its maximum height? b) calculate the maximum height that the ball reaches? c)...
  37. B

    Calculating Air Flow Rate for Floating Ball in Vertical Pipe

    Hi all, I am working on a prototype and I have a question that I am not sure how to answer, thus the reason I am here. I have a piece of 4" pipe that I will vertically mount and I am reducing down to 1". Inside the tubing I have a racquetball. I am going to be sending air through the...
  38. M

    Every closed ball in X is complete, then X is complete

    Homework Statement . Prove that if every closed ball in a metric space X is a complete subspace, then X is complete. The attempt at a solution. Let ##\{x_n\}## be a cauchy sequence in X. Then, for ##ε=1##, ##\exists## ##n_0 \in \mathbb N##: ##\forall## ##m≥n_0##,##n≥n_0##...
  39. icesalmon

    Projectile motion of a ball thrown

    Homework Statement Julie Throws a ball to her friend sarah. The ball leaves julies hand a distance 1.5m above the ground with an initial speed of 23m/s at an angle of 26° wrt the horizontal. Sarah catches the ball 1.5m above the ground. (a) what is the horizontal component of the balls...
  40. P

    Throwing a ball and calculating the speed

    Homework Statement A person with a 3 kg ball at rest in his hand, throws it with constant force at an angle of 45 degrees. The ball moves in a straight line until it leaves his hand at 2.1 meters above the ground. His arm has the length of 0.55 meters. Between the ball leaving his hand and...
  41. C

    MHB Find the average speed of the ball

    the height in ft of a baseball, t seconds after being thrown straight upward, is given by h(t)=36t - 16t^2 1) find the average speed of the ball for a) 0≤ t ≤1 b) .5≤ t ≤ 1 c) .9 ≤ t ≤1 the answer to a) is 20 ft/sec, which is what you get if you plug 1 into the equation. the answer to b)...
  42. H

    Same Speed for Ball Thrown from Moving Car?

    We have two people. A person(A) that is stadning and another(B) one who drives his car,so he has some velocitty. Let's say that the person B throw a photon from his car. Let's suppose that photon will hit down and will go up again. So both guys see the same speed. But If instead of light,he...
  43. S

    Motion Diagram of Galileo's Ball Drop from Leaning Tower of Pisa

    Homework Statement Draw a motion diagram for each motion described below. -Use the particle model -Show and label the velocity vectors 22) Galileo drops a ball from the Leaning tower of Pisa. Consider the ball's motion from the moment it leaves his hand until a microsecond before it hits...
  44. P

    How High and Far Does a Soccer Ball Travel When Kicked?

    Neglect air resistance for the following. A soccer ball is kicked from the ground into the air. When the ball is at a height of 10.07 m, its velocity is (vx,vy) = (4.63,3.83) m/s. To what maximum height will the ball rise? What horizontal distance will be traveled by the ball? With what...
  45. Crazymechanic

    Ball lightning atmosphere interaction

    There are numerous threads here about ball lightning but I am not exactly sure have any of those addressed this issue? Now a ball lightning even though haven't been duplicated in the lab is most likely a some sort of sphere or form of a plasma or ionized gas that has to do with charges and...
  46. S

    Magnetic moment of a solid, uniformly charged ball

    Homework Statement Show for a solid spherical ball of mass m rotating through its centre with a charge q uniformly distributed on the surface of the ball that the magnetic moment μ is related to the angular momentum L by the relation: \textbf{μ} = \frac{5q}{6mc}\textbf{L}Homework Equations μ...
  47. A

    What is the speed of the ball when it leaves Sarah's hand?

    Homework Statement The question I am struggling with is the second version of a similar problem so to make it easier for me to receive assistance, I'll post both parts: Julie throws a ball to her friend Sarah. The ball leaves Julie's hand a distance 1.5 meters above the ground with an...
  48. B

    BALL DROP EXPERIMENT: calculation of the magnitude of G

    I plotted the distance in cm ( y2-y1) versus the average change in time squared. (This had to be done by hand...) Then I had to find the slope and the y-intercept. Then I was asked to, " ... From your slope, find the magnitude of the acceleration due to gravity (g)" ... I am really...
  49. M

    Velocity Calculation - ball bouncing off a wall at an angle

    Velocity Calculation -- ball bouncing off a wall at an angle Question: "A ball is locked at 45 degrees towards a wall at 4 m/s. It bounces away from the wall at an angle of 45 degrees at 3 m/s. Find the change in velocity of the ball at the bounce." My attempt: So I know that change in...
  50. S

    Solving Ball Bearing Problem: Tower Height & Impact Velocity

    Hi, I was Googling about the following question : "Ball bearings can be made by leting shperical drops of molten metal fall inside a tall tower - called a shot tower- and solidify as they fall. If a bearing needs 4.0s to solidify enough for impact, how high must the tower be? What is the...
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