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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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Q: Inelastic collision homework [on hold]

Here's the original question: Two cars travelling in opposite directions at 36 m/s collide head-on and lock together. One car has the mass of 1000 kg; other has a mass of 800 kg. What is the speed ...
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2answers
48 views

Why can I not conserve kinetic energy in the following case? [on hold]

For the 2nd part of the question, if I conserve angular momentum about the centre of mass of the rod I get one value, and if I conserve kinetic energy of the rod and ball system before and after ...
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0answers
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How much more damage is caused after hitting a brick wall at 100mph over 50mph? [duplicate]

How much more damage is caused after hitting a wall at 100mph over 50mph? It is clear that there is just twice as much force generated after hitting a wall at 100mph, since the deacceleration is twice ...
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2answers
44 views

Finding 3 unknowns in 2D-collision problem [on hold]

While solving a 2D-collision problem, I obtained the following 3 equations: $$0.866\,|\vec v_{Af}|+|\vec v_{Bf}| \cos \theta_{Bf}=6$$ $$0.5\,|\vec v_{Af}|+|\vec v_{Bf}| \sin \theta_{Bf}=0$$ $$|\vec v_{...
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1answer
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Invariant mass in special relativity [on hold]

I'm following a special relativity course and I'm trying to understand how the invariant mass works. In particular I don't get how the following passages work. We have a collision between two ...
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5answers
518 views

Why does energy conservation give me the wrong answer in this inelastic collision problem?

Suppose there are two objects. The first object is stationary and has the next parameters: v1=0 m/s, m1= 4kg. The second object is heading towards the first one with speed v2= 8m/s and mass m2= 60 kg. ...
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1answer
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Can a projectile bullet kill? [on hold]

Today, I was watching a movie, in which a person shot a gun in air. The bullet went high in sky, became stationary for a moment and dived back and killing a non-innocent person by hitting him in head ...
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Find number of collisions [on hold]

A ball dropped from a certain height,falls in the influence of uniform gravity,strikes the ground and rebounds elastically.During a time interval t=8s from it was dropped,it covers a distance s=20m....
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4answers
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How can momentum but not energy be conserved in a collision, if objects keep moving in the same direction?

For example, there are 2 objects with the same mass, moving in the same direction, one with speed 5 m/s and the other 1 m/s. They collide and keep moving in the same direction, now one with speed 4 m/...
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1answer
40 views

Conserved quantities in ballistic pendulum

A bullet of mass $m$ hits a sandbag of mass $M$ that is suspended from the ceiling by a massless rope. At the moment the bullet hits it has a horizontal velocity $v$, and it gets stuck in the sandbag. ...
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1answer
35 views

How can a hammer of very less weight apply a large force when hit from a height?

Consider a hammer of weight 20N . When it is at on the table the only force it can apply on the table is it's weight. so it applies 20N when kept on the table . But when it is raised and dropped, the ...
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0answers
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Proton and electron collisions [closed]

A proton moving with a velocity $\beta c$ collides with a stationary electron of mass $m$ and knocks it off at an angle $\theta$ with the incident direction. Show that the energy imparted to the ...
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2answers
33 views

Real life elastic collision and variation of kinetic energy

How small should $\Delta T$ be in a collision to be considered elastic? In elastic collisions $\Delta T =0$, but as far as I know, just atomic collisions are considered perfectly elastic. Then, which ...
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0answers
57 views

Quantum mechanics paradox

Let us consider a collision problem of two particles 1 and 2. After collision we measure the position of the 1st particle and momentum of the 2nd particle simultaneously. Now from momentum ...
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3answers
61 views

How does conservation of momentum work here? [closed]

Imagine 2 oppositely charged particles attracted to each other, say an electron and a nucleus, assume their force of attraction is very large compared with any external applied force we're about to ...
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1answer
77 views

Relativistic collisions (elastic) - stationary target, equal mass [closed]

I believe it is more of a conceptual question than a homework question. A moving electron with energy $E$ hits a stationary electron. Question is to find the scattering angle (the angle between the ...
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1answer
17 views

Mechanics of a stationary grain resting on the surface of a granular bed which is subject to a collision

Consider the following stationary configuration of three disks (in 2d): I would like to consider the two supporting (lower) disks as entirely static, but the upper disk can move, and it only rests in ...
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1answer
41 views

Elastic collision between a circle and a point [duplicate]

In a 2D environment, I have a circle with velocity v, a stationary point (infinite mass), and I am trying to calculate the velocity of the circle after a perfectly elastic collision with the point. ...
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0answers
23 views

Restriction for the rule: change in momentum=force x time?

I did a prac about impulse and momentum. F∆t=m∆v indicates that the change in momentum should same as the area under force time graph. I ran a experiment where a cart is released on a slope and hit ...
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1answer
31 views

Calculating velocities of 2 squares after collision

If I have 2 squares each with random velocities, and both with the same mass, would it be possible to calculate their velocities after a collision, and how would I do so?
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1answer
56 views

Which formula for elastic collision?

When researching a bit about elastic collisions, I've been confused about how many different ways there are to do this. I've seen multiple methods, some of which are extremely complex (using sine and ...
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2answers
57 views

What work is done by the wall when a ball hits it?

So, in my physics textbook it's written that the kinetic energy possessed by a body is equal to the amount of work done by an opposing force to stop the body, now that got me thinking that when a ball ...
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1answer
33 views

Which is more important for a force of the impact mass or velocity? [duplicate]

If a 2 times bigger mass collides with an object in which a 2 times smaller mass collides but with 2 times the speed which one will produce more force on the object? The object is stationary before ...
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1answer
39 views

Impulse imparted during elastic collision [closed]

Lets say there are two objects a of 1kg and a very heavy block. The light mass has a velocity of $12$ $ ms^{-1}$ towards right. The heavy block has a velocity of $10$ $ ms^{-1}$ towards right. The ...
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1answer
44 views

Inertia of a falling weight

I use a standard device (penetrometer) that uses a 10 kg weight that is dropped a constant distance to cause a probe to penetrate soil. The penetration distance after 4 blows is recorded. If I were to ...
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3answers
861 views

Why do objects rebound after hitting the ground? [duplicate]

When an object, say a shoe, falls from a height (under the influence of gravity), it rebounds after hitting the ground. For an object to move upwards, it requires a force to overcome its weight. When ...
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1answer
49 views

Mathematical expression of impulsive forces during a collision

I'm facing with problem regarding collision between bodies. Specifically, I need to understand the impulsive forces that arises during a collision. Sometime ago, I posted two questions (this and this) ...
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2answers
44 views

Falling from a high cliff [closed]

I've always wondered about the reason why falling from a high cliff could actually cause death, is it the normal force exerted back from the ground? or is it related to energy? or what? thnx.
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1answer
52 views

Predicting elastic collisions [closed]

I want to predict how a collision will go with physics. Say I have a perfectly elastic 1-dimensional system with a frictionless ground and two objects of masses say $m_1$ and $m_2$ moving with ...
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1answer
41 views

“Plushness” of a simple mechanical damper?

What heuristics generally define the "plushness" of a mechanical damping or braking system? For example, if a person or some mass is to collide with a fixed wall or the ground (e.g., after a vertical ...
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1answer
70 views

I have a pair of magnets that when I let go they attracted and broke

I let two magnets attract from a distance and when they hit they both broke a piece off of each-other. Why did the magnets damage each-other when they collided and is it possible to put the broken ...
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1answer
81 views

Merging black holes — how fast do they hit?

Orbital mechanics says something falling from infinity hits at the escape velocity of the object it strikes. The escape velocity at the event horizon is lightspeed, it must be higher for the ...
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0answers
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How do big black hole kicks out small black hole?

I read that when 2 black holes collide they will either merge into a single black holes or recoil and the less massive black hole will be thrown out, I'm thinking of gravitational slingshot whereby ...
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1answer
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Why don't merging black holes disprove the no-hair theorem?

The no-hair theorem of black holes says they're completely categorised by their charge and angular momentum and mass. But imagine two black holes colliding. At some point their event horizons would ...
3
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1answer
58 views

Kinetic theory of gas. Pressure in a container derivation feels wrong

NOTE: Please Imagine A cube with 2 parllel faces I and II lying along the x axis. In the derivation what we are thought Change in the momentum of the molecule = Final momentum - Initial momentum =...
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1answer
31 views

How do I find the direction of impulse vector in a collision?

I know that impulse is the change in linear momentum. Is the direction of impulse always along the change in momentum vector? Please explain.
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3answers
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In particle colliders, according to QM, how are two particles able to “collide”?

According to QM, we know that The act of measurement forces a particle to acquire a definite (up to experimental errors) position, so in a particle collider, like the one in CERN, by which means ...
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0answers
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Application of Kepler's law [duplicate]

Suppose two equal and opposite charges are released from a relative separation of $d$ in free space. How long would it take before they collide? I believe we can use Kepler's law of T² being ...
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1answer
36 views

Pion decaying energy

The question is: A pion decays into a muon and a neutrino (which is almost massless, so we’ll take it to have a mass of zero). If the pion is initially at rest, find the energy of the outgoing ...
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1answer
63 views

Is it correct to use Newton's third law on all these scenarios? [closed]

So I was thinking about Newton's third law for sometime lately, and my problem is more about the concept, I'm fine with solving problems. I thought of these scenarios and tried to apply Newton's three ...
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1answer
49 views

Two solutions of collision problem. Which is correct?

I'm solving a 1D problem, in which a particle with mass 2m collides elastically with a particle of mass m. Both of them have a speed V. After setting up the equations I've reached a quadratic ...
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0answers
25 views

$F_n$ force between 2 objects in space

I am trying to do a research project for school where I'm trying to simulate the physical world in a computer environment. So far things have been working great but I have trouble understanding how ...
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0answers
17 views

impulse in inelastic collision in two dimensions

I'm trying to find the impulse in an inelastic collision of two particles.At the end of this page there is formula for that.But I cant reach it bu my own.Here is what I think is the way to find the ...
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1answer
41 views

Centre of mass collision

A proton with momentum 3 GeV in LAB frame of reference is difussed elastically by a stationary proton. The angle of diffusion of one of the protons, in the CM system is 10º, corresponding to a moment ...
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2answers
51 views

Two bodies, one with mass m and the other with very very huge mass (tending to infinity), moving with velocity v and -v (opposite directions) collide

Assumption: The bodies are moving on the same axis, along their center of mass, and the bodies are perfectly spherical. There is no loss of kinetic energy after collision. m2 >>> m1 v2 = -v1 Will ...
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1answer
40 views

3D perfectly elastic collision between two points

There is a high probability, I think, that this question is a duplicate of some other question ... but to may knowledge, it hasn't been posed in this exact manner: Assume we have 2 points, $P_1$ and $...
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1answer
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Particle collision and mass relation [closed]

Is mass important in calculations when two particles are collide? or is only the charge that matters? is collision in microscopic world the same with macroscopic world?
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2answers
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Collision between two objects where the center of mass never moves

I had the following problem: Image two cars approaching one another in opposite directions. The first car is twice as massive as the second car. They move so that the center of mass of the two-...
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1answer
37 views

Momentum of projectile in the centre of mass frame in a two body system

The COM frame is defined as the coordinate system in which the centre of mass of the system is at rest. In the case of a 2-body system the center of mass coordinate is: $$\vec{R_{CM}} = \frac{M_A \...
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0answers
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Why are there no excitations by collision for the visible transitions in the Franck-Hertz experiment?

The minima of the I(V) graph for a Neon Franck-Hertz tube are approximately 20V apart from each other, this is usually explained by the fact that excitation by inelastic collision happens at about 20 ...