Questions tagged [collision]

Interaction between two or more bodies that results in physical contact and an exchange of momentum between the bodies involved.

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2answers
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Why is the center of mass the pivot of rotation?

Suppose a ball moves horizontally to the right and hits a vertical stick at a position closer to its upper end. I understand intuitively, the stick will have linear and angular momentum, and that it ...
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1answer
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Calculate impact force. when A beam starts to fall down with one end hinged and hits an object [closed]

A beam of 10 Kg and length 12 meter starts to fall from initial vertical position with one end hinged. When Beam's center of mass is dropped 5 meter from earlier position, Beam hits an object with ...
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Rotating triange colliding with wall

Imagine a freely moving equilateral triangle in the x-y plane with a given velocity $\vec v$ rotating around the z axis at its center of mass with an angular velocity $\vec \omega$. Now this triangle ...
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Could we make a orbital kinetic strike weapon big enough to destroy a city? [closed]

i was playing call of duty ghost recently and i realized they were using a kinetic orbital strike weapon and i was just wondering if it would be possible and effective at the same time I've watched a ...
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Black holes and FTL particles [duplicate]

I Was wondering, since a black hole generates enough gravitational pull to overpower light speed, does that mean anything in a black hole past the event horizon travels ftl? If 2 black holes each ...
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1answer
60 views

Calculate maximum force in elastic collision between carts

Consider two carts, one of mass $m_1$ moving frictionless to the right with velocity $u_1$ and then colliding elastically with a second cart with mass $m_2$ initially resting $u_2 = 0$. Since the ...
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How to determine if two objects collide or not using maths? [closed]

Imagine any two objects in space among which one is in motion while the other in rest and let's suppose that they move towards each other. Now can one say that the objects collide with each other if ...
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How is momentum conserved during the short period of time during collision when there is no kinetic energy and only potential energy?

We know that in an elastic collision , momentum of the system is always conserved. But during the short period of time during collision when there is no kinetic energy and only potential energy how is ...
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Why doesn't Newton's third law mean a person bounces back to where they started when they hit the ground? [closed]

When we drop a ball, it bounces back to the spot where we dropped it, due to the reaction forces exerted on it by the ground. However, if a person falls down (say, if we push them), why don't they ...
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221 views

Collision between 2D circle and flat surface [closed]

First of all I want to preface this post by saying that I am absolutely terrible at maths, my level of geometry equals being able to discern a circle from a rectangle but that's about it, as for ...
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where is the best bounce on a racquet?

I am dropping a ball on a racquet, measuring bounce height against position. And the results are a bit all over the place. I found 3 places on the racquet that make the ball bounce higher. I read ...
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Is the Momentum conserved? [duplicate]

I was trying to solve a simple problem regarding a particle being launched by an angle theta where it hits a rod, we have: a) System(Particle, Rod) b) System(Particle, Rod, Henge) My question is when ...
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Are impacts in outer space more powerful than on Earth? [duplicate]

Is an impact less destructive on Earth than on other planets with no atmosphere, given that the momenta, factors like the line of impact are identical in both cases? If yes, then is it because there ...
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4answers
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Momentum is not conserved during inelastic collision?

When considering room as a system, when a ball is made to fall freely and it collides with the floor it loses speed each time it collides. The momentum hence is not conserved in this case? Can anyone ...
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Combining two coefficients of restitution

The coefficient of restitution tells you how the velocity of an object changes after a collision due to losses. If $v$ and $v'$ are the relative velocities before and after the collision then $$e=\...
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Is Atmospheric Pressure due to weight of air or the collisions of the Molecules

This question is in response to @brightmagnus answer whose link is Pressure in Fluids,in particular horizontal pressure The question : Is the atmospheric pressure due to the weight of air or ...
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4answers
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If a ball is thrown to a person standing on a frictionless surface, is the impulse of the thrower equal to that of the catcher?

If a person throws a ball, exerting a given impulse does the person that catches the ball receive the same impulse assuming that the catcher moves. Is the impulse that the catcher receives less than ...
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Macroscopic object grazing the event horizon of a supermassive black hole

Just a noob question: They say, when you dive into a heavy/large enough (supermassive) blackhole, there should be nothing wrong with you at the time of touching an event horizon. I suppose it's a ...
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1answer
65 views

The Physics behind “The Wall” Game show ball drop

In "The Wall" game show, the slots and also the diverters are designed symmetrically and also identically. So when a ball is dropped from a particular slot number it should end up in a particular ...
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1answer
27 views

Collisions in a System of Bodies

There are three blocks A,B and C, with B and C at rest connected by a light spring and A moving with a velocity v, all three lying on the same horizontal frictionless surface. After some time A ...
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What would happen if a black hole swallowed a white hole? [duplicate]

I’m just curious on this, if you can tell me then please do. Also don’t shame me for my bad question I’m just a curious little fella!
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2answers
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Does a higher velocity make a collision more or less elastic? Does it have any impact on it at all?

Basically, if you increase the velocity before the collision, does the collision become more elastic? If you used conservation of energy as proof, (i.e the faster the velocity, and the less percent of ...
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When does a collision become classical?

I was thinking (after misinterpreting and answering another question) about collisions on the atomic scale. I know it's impossible to visualize, but I did. For example the collision between an ...
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4answers
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Newton's third law of motion confusion [closed]

Suppose, there are two objects, namely, A and B. Suppose, object B is more fragile than A, such that it breaks on the application of a 5N force. If A is accelerated such that the force carried by A is ...
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1answer
406 views

What is the average value of time since last collision in Drude model?

I have been following Feynman lectures on Physics, lecture 43 — Diffusion. There he derives the average value of time till next collision over all molecules. He finds it to be equal to the average ...
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Collision and conservation of momentum

I was considering a situation where a bullet was shot at an angle and lodges itself into a block and then the to move as a system. As usual, I figured I could solve for the final velocity of the ...
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472 views

Calculating the total time elapsed until two pendulums “stop colliding” gives a divergent result [closed]

Setup Consider the following situation: Two (small) balls hang by two identical ideal threads, such that in their initial states the threads are perfectly vertical. The two balls are moved by small, ...
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163 views

Elastic collision question [closed]

I have a simple elastic collision question. In a perfectly elastic collision between equal masses, can the mass with a slower speed transfer energy to the mass with a faster speed? No constraints ...
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52 views

Newtonian-Mechanics .Elastic reflection [closed]

Question from the olympiad. Two planes move perpendicular to each other with speeds $v = 1m/s$. A body flies at them with a velocity of $u = 1 m/s$ at an angle $a=45$ to the surfaces of the planes ...
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133 views

Calculating temperature of objects after colliding

So, I'm making a physics engine, and I need to know what is the temperature object A has after colliding with object B. Object A is 10 earths in diameter, and is 10 earths in mass. Object B is 5 ...
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In an electron-positron annihilation, in what direction are the photons released?

I read that, in an electron-positron annihilation, at least 2 photons are produced, because of the law of conservation of momentum. my question is: in what direction are those photons released? and ...
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Conservation of Mechanical Energy in Collisions

The Law of conservation of Mechanical Energy states that in a closed system with no non-conservative forces acting, the energy of the system will always remain constant. This makes sense for an ...
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Derivation of collision term in Boltzmann equation: Trying again [duplicate]

Can anyone show me a derivation of the collision term in the Boltzmann equation? I don't mean one of the simplified varieties. I mean Boltzmann's full-blown term as here. Update: I asked this ...
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What causes damage, kinetic energy or momentum?

Let's assume we have 2 bullets. The first bullet has $450$ $J$ of KE and $3$ $kg.m/s$ of momentum, while the second bullet has $250$ $J$ of KE and $5$ $kg.m/s$. Now if they are both shot at ballistic ...
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Would a group of molecules in a container, settle down after a long time? (considering that no gravity acts on them) [duplicate]

Because, every time they collide, don't they emit radiation? As in, losing energy in the form of this radiation, So eventually, won't they lose all of their kinetic energy? Of course the time taken ...
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2answers
197 views

Colliding black holes

If objects approaching the event horizon of a black hole appear to slow down to outside observers, how was LIGO able to "see" black holes collide? Wouldn't their collision appear to stop as their ...
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4answers
583 views

What is more harmful in a car crash - restrciting movement or allowing some movement to reduce g-force?

Sorry if I haven't worded the title very well, feel free to improve. Let me explain before I ask my question... We have purchased a car carrier (small version) for our dog and also purchased some ...
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1answer
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Effect of object mass in coeficient of restitution

I know the coefficient of restitution depends on the velocity before and after the impact of a bouncing ball. How does the mass affect it. Can't figure it out. v ...
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1answer
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Equivalency of conditions involving angular momentum of a rolling ball hitting a wall

(59th Polish Olympiad in Physics) A ball of mass $m$, radius $r$ and a moment of inertia $I = \frac 25 mr^2$ is rolling on the floor without sliding with the linear velocity $v_0$. It hit the wall ...
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Deformation of an elastic ball

Suppose a free sponge ball is being compressed, due to applying a known force in a specific direction. The ball's shape will be distorted. Given are the direction of the applied force, as well as its ...
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1answer
263 views

Predicting contact time and COR (coeff of restitution) for a cricket ball and pitch

For real world application, COR --> Bounce produced by pitch, for both spinners & seamers; Contact time --> grip provided by pitch, mainly for spinners Assuming cricket ball to be a sphere and ...
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2answers
750 views

Calculating the Coefficient of Restitution Based on two Objects

The coefficient of restitution is calculated based on the velocities of objects before and after a collision: $$C_R = -\frac{v_{2f} - v_{1f}}{v_{2i} - v_{1i}}$$ The coefficient of restitution tells ...
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Why is momentum conserved in an inelastic collision and kinetic energy is not conserved? [duplicate]

We know that in an inelastic collision that total momentum of the system before collision equals the total momentum after collision. But total kinetic energy before collision is not equal to total ...
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1answer
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On defining mass scales using collisions

In A.P. French's Newtonian Mechanics (pages $319$, $320$), the author described a way to define a scale for masses. He said, One can set up an inertial mass scale for a number of objects $1, 2, 3,…$...
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142 views

Collision of Rolling body

When a rolling body collides with a wall elastically,its torque is zero.But direction of velocity of particle is reversed.So will the angular momentum be conserved?
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Conservation of energy in collision if A hits B but fails to move B

If body A hits body B but fails to move B what happens to its kinetic energy? There is no increase in potential energy. So what is accounting for this loss?
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Is kinetic energy always conserved in an elastic collision/impact?

While working out through some problems I encountered this problem : A ball moving with a velocity $v$ hits a massive wall moving towards the ball with a velocity $u$. An elastic impact lasts for ...
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2answers
44 views

Conservation of angular momentum in a collision using quantum mechanics

In an undergraduate course in particle physics we are learning about angular momentum conservation. In particular, at some point we analyzed the colision between a pion ($J=0, p=-1$) and a deuteron ($...
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Why do objects always stick together in perfectly inelastic collisions?

From what I understand, perfectly inelastic collisions are those in which the maximum possible amount of kinetic energy is lost from the system. This means that the kinetic energy after the collision ...
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2answers
149 views

Momentum conservation in a small time interval

I recently solved a problem in which I used the "fact" that the momentum is conserved just before and just after a collision between two (or maybe more) objects but I am not sure whether this is true ...

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