# 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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### Physics of a punch

So I have odd question revolved around karate and would love to know if my physics assumptions are correct. Basically I would like to know what equation to use to calculate the force of a punch when ...
192 views

### What is happening from electro-magnetic point of view when a proton and an anti-proton annihilate?

Purely electro-magnetically before a proton (+) and an anti-proton (-) annihilate each other /assume they do/, they form a dipole. What happens after that? In other words, what does an external ...
6k views

### Is there anything in the universe that cannot be compressed?

I've always thought that there is nothing in the universe that cannot be compressed or deformed under enough force but my friend insists that elementary particles are exempt from this. My thought is ...
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### Is there any different how we smash antimatter and matter together?

Imagine: Setup A, we smash relativistic electron at a stationery positron. Setup B, we smash electron and positron head on both moving at fraction of speed of light. Setup C, we allow electron to ...
889 views

### Modelling elastic collisions and reflection from wall in 1D box of two particles

I have a very simple system of two particles. Particle $A$ and particle $B$. Particle $A$ is acted by constant potential along wall $C$ while no potential is acted on particle $B$. If they both ...
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### Question About Collisions Between Neutrons

I came across this question from AP Classroom that asked something along the lines of, Neutron A was traveling at velocity: $v$ and has wavelength $\lambda$. It then hit neutron B and after the ...
268 views

### What happens to a softer material hitting a harder material at high speeds?

You often see action scenes in media, where a person is thrown so hard against a concrete wall, it breaks. My question is if it's possible for a softer material to be accelerated to point where it ...
91 views

### When a ball hits the wall, the higher the speed of the ball is, the stronger the ball exerts a force on the wall

I am reading an elementary mechanics book and I have the following question now. When a ball hits the wall, the higher the speed of the ball is, the stronger the ball exerts a force on the wall. ...
30 views

### How can I find the Final velocity of the System (if perfectly inelastic) Ignoring air resistance [closed]

I am given that a bullet of mass 24.6 grams is shot at a block of 231 grams that will slide on a wooden desk with a coefficient of kinetic friction being .210. all i'm given is that the block more 32....
158 views

### How to calculate time at which two circles will touch?

Hopefully this is the right... Stack to ask this at. Apparently there are a bunch of them. I'm trying to find a formula to detect the time at which two circles in a 2d plane will touch. I'm given the ...
701 views

### Calculating the force of someone falling backwards

Say someone was standing and fell backwards. Knowing their mass and height, would it be possible to calculating the force they hit the ground with, not accounting for air resistance? What I've tried: ...
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### Is the speed of recession equal to the speed of approach for any elastic collision?

I am comfortable with the idea that in a one-dimensional elastic collision, the speed of approach of the two colliding bodies is equal to the speed of recession following the collision, which can be ...
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### What happens when a weapon breaks on impact?

Here is the situation: You are attacking someone with a wooden pole (such as a pole arm or tree branch). You either (1) hit as hard as you can and the pole breaks into two pieces on impact OR (2) hit ...
105 views

### An asteroid strikes Earth. I’m skydiving. Do I die? [closed]

Let’s say I’m skydiving at a high altitude and, while falling, an asteroid strikes Earth. Is there a certain mass / momentum of the asteroid below which I would have a chance of surviving? Or would ...
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### Which collision equation is appropriate to use?

Take this example problem: A 2 kg ball moving east at 3 m/s that enters in collision with another 1 kg ball moving west at 2 m/s. After the collision, the 2 kg ball has an eastward speed of 10 m/s. ...
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### Why the rubber ball bounced higher than the glass ball?

For a teaching degree we did the following experiment: Drop a rubber and a glass ball of approx. same size from approx. same height onto laminate flooring. As we expected, the rubber ball bounced ...
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### Elastic Collisions - Equation not working?

This is the question: When cars are equipped with flexible bumpers, they will bounce off each other during low-speed collisions, thus causing less damage. In one such accident, a 1850 kg car ...
97 views

### 2D collision of round objects; Is this correct? [closed]

I'm creating a collision simulator for round objects. I've written out the physics and I just wanted to ask if it's correct. Are there any parts I should change, or any way to simplify it more than ...
79 views

### Can we find coefficient of restituion using Young's Modulus

Suppose a moving body collides with another body and we are given the Young's Moduli of the two bodies. Is there any method to find their final velocities?
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### Dynamics collisions - reduced mass [duplicate]

In dynamics when doing collisions from the centre of masses' frame of reference we use reduced mass. What is is it and why do we use it?
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### Conservation of energy when ball rebounds

Consider a ball that strikes a stationary box and has momentum $mv$. If the ball rebounds with the same speed it had before the collision, its momentum is $-mv$. Therefore, the box must have a ...
68 views

### Does universal proof exist for newton's experimental law for all cases of elastic collisions?

Newtons experimental law I. E velocity of approach is equal to velocity of separation (for the points on the two bodies where the collision takes place) for an elastic collision is applicable for ...
27 views

### Is it normal to assume equal impact time?

If we have two hammers of different weights both hitting an object with the same force can we assume they both have the same impact time?
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### How does the force on a crashing train relate to its velocity and the area of the train that is touching the wall?

I am modelling the crashing of a train with a deformable crumple zone on the front. I am assuming that the crumple zone deforms from the front back, so I am essentially modelling it as if the crumple ...
10k views

### The momentum of a swinging sword

Suppose you are faced with a zombie, and the only way to kill it and save yourself is to chop its head off with your sword. However, you are very weak from illness, and can only afford to strike once. ...
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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. ...
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### How can kinetic energy increase during a collision?

The below homework question just sets the context for my question. I am not asking for a solution to this question In a collinear collision, a particle with an initial speed $v_0$ strikes a ...
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### Elastic collision between a point and a rotating solid

Consider a pointwise particle with mass $m_1$ and speed $v_1$, which collides with a solid $S$ of mass $m_2$, rotational inertia matrix $J$, speed $v_2$, and rotational velocity $\omega_2$. I denote ...
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### General Relativistic version of unorthodox two classical point particles collision problem?

So I was playing around with an idea but got stuck. Premise Imagine there are two classical point particles. I was wondering how would one talk about a collision and came up with something ...
182k views

### How can momentum but not energy be conserved in an inelastic collision?

In inelastic collisions, kinetic energy changes, so the velocities of the objects also change. So how is momentum conserved in inelastic collisions?
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### Conservation of momentum: Collision involving Tenis ball on top of Basket ball

I am asking about this video where The Physics Girl drops a system of balls from a height. I am trying to estimate the velocities just after the collision using the law of conservation of momentum. ...
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### Can someone explain what is the force the ball will exert?

If a ball is falling under free fall then the force exerted by the ball on the ground would be $mg$. But that's not the case in real life ball would hit with more force. But when i draw free body ...
44 views

### Do individual rest masses change in a relativistic elastic collision?

Consider a classical isolated relativistic elastic collision of two free scalar point masses in 1 D. The aim is to get the final velocities of the particles given initial rest masses and initial ...
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### Radiation from collision of two charged particles

Consider a collision between two electrons. Since each particle is accelerated during the collision, I assume each radiates energy according to the Larmor formula. Question 1: How much energy is ...