# 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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### Why is the loss of energy maxed in perfectly inelastic collision?

I was doing a physics problem, and it had asked me to find the maximum $K_e$ loss, but I don’t understand why the loss is maxed when the objects stick together (the collision is inelastic).
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### Changing up Newton's cradle

My professor explained Newton's cradle and then gave us the question: if you taped together the last 3 balls and pulled up and let go the first one, nothing would move on the other end but momentum is ...
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### COM frame for photons

We know that there is no frame in which the energy of a photon is zero and hence it has zero momentum. But can we find a frame in which the energy of two head on photons is zero, or the center of mass ...
0answers
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### Can hypervelocity impacts be an efficient EUV source?

Imagine that two small pieces of rock hit each other at a very high velocity (for example, small meteoroids moving at orbital velocity in opposite directions). How much of the impact energy could be ...
4answers
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### What would the collision between a (large) solid planet and a gas giant be like?

Assuming a Jupiter-like planet and an Earth-like planet (Except, say... half the mass of Jupiter), what would happen when the two collide? For clarification: What would the actual collision be like? ...
1answer
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### Where does the extra energy come during superelastic collison

It is known that in superelastic collison the energy of particles after collison is more than the original particles but how is it possible . I barely could find suitable information on net for a high ...
1answer
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### How to formally write down the Boltzmann equation?

Can someone write down the Boltzmann equation, not neglecting any of the variables of the involved functions and integrals? Specifically, how to concisely capture the "primed" variables in a sensible ...
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### Why do inelastic collisions occur in theoretical calculations?

When solving collision problems related to the conservation of momentum in my applied maths course, the question of whether the collision was elastic or not is often asked. A lot of them time (such as ...
2answers
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### Can particles gain energy during inelastic collision?

We know that when two particles collides inelastically, the net energy equation is given by $$E_i=E_f+Q$$ where $E_i$ and $E_f$ are initial and final mechanical energies of the particles and $Q$ is ...
0answers
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### Is Jupiter really protecting us from collisions with objects?

Many documentaries I see on the Solar System or the planets or the threat of collisions with meteorites talk about how lucky we are to have Jupiter, with its immense gravity attracting asteroids to it ...
1answer
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### Most fundamental reason for Newtonian KE loss being invariant in inelastic collisions

This answer to a question about why Newtonian kinetic energy is quadratic in velocity shows that if an inelastic collision's KE loss is invariant under Newtonian boosts it has to quadruple when ...
3answers
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### Why the relative motion goes wrong here?

This is a question from jee advanced. I followed the approach of relative velocity In the frame of rocket we can write $s_{rel}$=$u_{rel}t$ since acceleration of both the particles is 0 in this frame ...
2answers
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### Does mechanical energy remain constant during an inelastic collision

Suppose two bodies collide inelastically, does the total loss in kinetic energy get converted into potential energy associated with the deformation? Or does the energy also transform into other forms ...
2answers
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### Two sonic booms colliding

If I theoretically created an experiment where I could create two sonic booms in directions such that the sonic "nose" is facing each other; what would happen? more specifically: Lets suppose I have ...
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### Why do I see two peaks in the KER spectrum of a Dinitrogen-electron collision?

I am currently reading a paper about an experiment, where they have a Dinitrogen atom and smash a 1000 keV electron into it. This results in a fragmentation where the Dinitrogen atom + the electron ...
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### Can projectile motion under gravitational fields be considered an example of collision?

It is given in my book that the scientific definition of collision is that two or more bodies are said to collide when their motion is affected by the force they exert upon each other. For Eg. When ...
3answers
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### Impulse of two different objects

I was running over a question, A collision occurs between particles A and B which are moving in opposite directions in the same straight line. The impulse on each particle in the collision is 2N.s, ...
8answers
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### Does momentum change when Kinetic energy changes?

$K.E=\frac{1}{2}mv^2$ , $P=mv$ thus there is a relation between them. I really can't understand why there is no decrease in momentum when kinetic energy is decreased in an inelastic collision. I am ...
1answer
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### Why is the angle made by the two bodies with the horizontal 45 degrees after collision?

A proton of mass $m$ collides elastically with a particle of unknown mass at rest. After the collision the proton and the unknown particle are seen moving at an angle of $90^o$ with respect to each ...
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### Do electron-electron collisions have an associated scattering cross section?

Various texts (1,2) state that electrons are point particles, but if this is the case then when two electrons collide, one of them knows the others position with exact certainty (treating one as an ...
1answer
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### 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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### Breaking point?

We all know when I hit glass with a stone, the glass will shatter, the stone will most likely survive. If I hit a rubber cube with the same stone, both would probably survive and I might get a stone ...
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481 views

### Why do we refer the cross section ratios to muons?

For electron-positron interactions, we have different cross sections, depending on the available reaction energy. To get an overview how many particles of a certain type have been created, we can ...
4answers
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### Conservation of Momentum with external force

If an object under a constant force , say gravity. Collides with another object with no external force acting on it. Will the momentum of the system right before and after the collision be the same if ...
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### Impact of a falling object on the surface

Suppose an object of 75 kg falls from a height of 2 feet on land. Normally the land will feel the weight on it as 75 kg. But when the object is fallen from a height it will have some speed so at the ...
1answer
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### Collision using Reduced mass [closed]

While reading a wikipedia article about collision using reduced mass I came across this. how has it been derived?
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### How to estimate the impact force of a martial artist breaking bricks?

I was watching a martial artist breaking a stack of 9 out of 10 concrete bricks. I noticed that the last didn't break. It made me wonder if this would allow calculating the force dealt to be ...
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### Lattice Boltzmann method: properties of D2Q37 stencil and beyond

I am new in the world of Lattice Boltzmann method (LBM). I have just found in this paper [1] the following statement: A D2Q37 Lattice Boltzmann scheme correctly reproduces the equation of state of ...
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I have been trying to understand absorption of a photon by a massive object, specifically the transfer of momentum and kinetic energy between the two. Starting from energy-momentum relation $E^2 = p^... 1answer 1k views ### Equivalency of conditions involving angular momentum of a rolling ball hitting a wall (59th Polish Olympiad in Physics) A ball of mass$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 ... 1answer 2k views ### 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 ... 2answers 1k 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 ... 3answers 41 views ### Condition for two points to collide with constant speed$v_1$and$v_2$at any point of time? [closed] We have been given the initial speed of 2 particles. They have a constant speed. At any point of time$t\geq0$, their positions are given by$i+v\cdot t$where$i$is the initial position of the ... 0answers 30 views ### Impulse of colliding billiard balls The wikipedia article for dynamical billiards states that one can model the billiard balls with the potential $$V(q) = \begin{cases} 0 & \quad q \in \Omega \\ \infty &\quad q \not\in \Omega \... 1answer 302 views ### Predicting contact time and COR (coeff of restitution) for a cricket ball and pitch For real world application, COR --> Bounce produced by pitch, for both spinners & seamers; Contact time --> grip provided by pitch, mainly for spinners Assuming cricket ball to be a sphere and ... 1answer 38 views ### Ball inelastically colliding into a bar [closed] There is a horizontal bar of length 10 \mathbb{m} and mass 1 \mathbb{kg} that is held up (somehow) in the earths gravitational field. A ball of mass 0.1 \mathbb{kg} inelastically collides ... 1answer 509 views ### Why a bullet leaves a hole on glass where stone makes scratch? When we throw a stone it breaks the glass with scratches. But when a bullet hits the glass it leaves a small hole(not always) . I want to know the specific reason behind making hole and scratch. 1answer 147 views ### Rod hits rod - angular and linear momentum I've been analyzing "ball hits a rod in space" type collisions, where speeding ball transfers part of its kinetic energy during elastic collision to the motionless rod, making it gain linear ... 1answer 72 views ### Derivation of the collision frequency of gas with the walls of container How can one find the rate of collision per unit area with the walls of a gas container given the distribution as$$d N\left(v_{x}\right)=N\left(\frac{m}{2 \pi k T}\right)^{1 / 2} e^{-m v_{x}^{2} / 2 k ... 3answers 41 views ### How long will it take for a projectile to be knocked off a wall? (See details) I am trying to calculate the impulse of an object that is thrown against a wall. Problem is, to calculate the impulse one needs to know not just the force, but also the time it takes for the momentum ... 2answers 523 views ### Usage of momentum conservation during collision of 2 blocks 1 connected to a spring (at rest) and other hitting with a velocity suppose I have 2 blocks say A and B which are connected by spring and at rest, and there is a third block C which is colliding with A, will it be correct to use momentum conservation equation on this ... 0answers 83 views ### 4-Momentum in Special Relativity [closed] I have been given the following question; A ball of putty of mass$m$travels at speed$v = 0.8$towards another ball of putty of mass$2m$, which is at rest. After the collision the balls are stuck ... 1answer 28 views ### Inelastic Collision of two balls [closed] Is it possible that two balls of the same weight collide (in 1 dimension) and then stay at the rest? How is such a collision called? What are all the possible situations (velocities of 2 balls of the ... 2answers 49 views ### Physics of an hypothetical animal attack (orca ramming through sea ice) Question: Could an aquatic animal weighing 5,000 kg and traveling at 55 km/hr break through solid 11cm-thick ice? Context: I am writing a story and want the physics to be as accurate as possible. I'd ... 2answers 103 views ### If a relativistic proton e.g.$\gamma=5\$ hits a stationary proton will this collision take all its momentum?

In classical physics when a billiard ball hits a stationary one of same mass it transfers all its momentum to it so becoming itself stationary while the other gathers their whole momentum. But what ...
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### Role of friction during Collisions

Normally, in questions of collisions, we tend to apply conservation of momentum (and in cases of elastic collisions, conservation of energy as well) and we usually ignore the frictional force acting. ...