# Tagged Questions

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

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### 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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### Rain drop sliding on car windshield

Problem Definition As shown in the figure below, an automobile is travelling horizontally in the rain with a constant velocity V. The windshield has a slope of θ. A raindrop with a mass of m, ...
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### Why do tops move opposite to each other when colliding, not tangentially?

When two well-balanced tops collide, they tend to bounce directly away from each, in other words along the line connecting their centers. Intuitively I would expect the tops to move tangentially, not ...
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### Motion after a collision of objects not involved in it [closed]

I'm confused about collisions where there are parts of the objects not involved in it. How do these parts move after the collision? I'll make an example. Consider a cart with an incline attached (...
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### Inelastic collision problem [closed]

A car of mass $1400$ $\mathrm{kg}$ moving south at $11$ $\mathrm{ms}^{−1}$ collides into another car of mass $1800$ $\mathrm{kg}$ moving east at $30$ $\mathrm{ms}^{−1}$. The cars ...
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### Free falling and bouncing back

My confusion arises with free falling body. For a free falling body the displacement ~ time graph has a kink (at the time when the body hit the ground ). at a kink point, a function is not ...
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### Elastic collisions and 90 degrees angles [closed]

Why is it that if the angle between the two objects that collided together is 90 degrees then it must be perfectly elastic? Is there any theoretical proof other than convention?
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### A cruise ship bumping against a lock gate [closed]

For my project, I need to create a lock gate which will be used for the Panama Canal. One of the many thing my teacher said, was that for the design of the lock gate, the gate should not fail when it ...
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### Collision between airborne stone and car

If two cars are driving with a certain distance from each other, and the tires of the first car makes a stone (from the asphalt) become airborne with a high velocity - towards the second car: The ...
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### Energy and Momentum: Impact

Boat A has just lost another race to Boat B. In a fit of rage, the driver of Boat A (mass = 500 kg) turns his boat towards Boat B (mass = 450 kg) which is at rest as the driver gloats over yet another ...
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### What formula do I use to calculate the force of impact of a falling object?

I am trying to calculate the force of impact of a falling object. I did my egg drop project. I dropped the egg from 10m with a mass of 126kg and with the velocity of 14.1 m/s. Which formula should I ...
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### Newton's third law & punching walls [closed]

N-law 3: if you punched a wall as hard and as you could, would it possible to retract your hand before the reaction from the wall could affect your hand less than if you wouldn't retract at all? ...
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### Can a tomato pierce a hole in a steel plate if only the tomato is travelling fast enough?

A tomato is travelling very fast towards a 1 cm thick steel plate. Let's say this happened in a vacuum, so that the air resistance wouldn't rip the tomato apart before it even hit the steel plate. ...
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### The basic probabilistic relation of collision theory

In "Classical Mechanics", John R. Taylor gives this basic relation of collision theory $$N_{sc}=N_{inc}n_{tar}\sigma$$ for firing projectiles into targets. $N_{sc}$ is the number of projectiles ...
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### Role of forces in this collision?

Consider two identical objects of equal mass collide with eachother with equal opposing accelerations. Wouldn't the forces of the objects cancel each other resulting in the objects both comming to a ...
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### Does the Inertia of a Cue Ball Affect its Reflection Angle off a Resting Billiard Ball?

Consider the following Diagram in which a Cue Ball (A) of mass M is shot twice at another pool ball with identical mass M. When the force with which the cue ball (A) is hit (v1) is increased (v2) ...
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### Question about 3d collision of 2 particles [duplicate]

I'm wondering about how to calculate the resultant velocity vectors of an elastic collision of two particles of same mass, in 3d. I've seen a post on the subject in which you answered, but I didn't ...
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### Proton-Proton collision [duplicate]

How are the people at CERN able to exactly collide protons head on? What about the HUP? Do they accelerate many particles and smash them so that at least some of them collide head on?
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### Does the physical cross section of a projectile have an effect on the motion of a target? [closed]

Why can a baseball (moving with kinetic energy) move a baseball glove (or how a hammer displaces a nail),. yet a bullet can't move a person? I know the laws of conservation of energy, deformation, etc....
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### Collision of moving large mass and small stationary mass?

Hypothetically if a mass, roughly the size of earth, was accelerating at 100m/s and came in contact with a 1kg stationary mass, due to newtons 3rd law wouldn't the small mass accelerate and the large ...
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### Total Momentum in the Center of Mass Reference Frame

For solving problems involving elastic collisions it is useful to use the center of mass reference frame as to avoid quadratic equations. However, I am confused about why the total momentum in the ...
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### What is the probability of two bullets to get clashed? [closed]

I was surfing on Instagram, and I found this amazing proto whose description is "the probability of such an event to happen is incredibly small, so this is a really curious finding". Well.. I'm ...
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### Gravity and force

I have a question and am not able to answer it. Suppose you drop two objects from different heights. They are exactly the same shape, size and weight. Now we know that the gravitational acceleration ...
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### What is the magnitude of a collision force?

First off, I want to clarify that when I refer to collision, I mean the situation in which two particles cannot be at the exact same position in the space. When two particles get closer and closer, ...
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### Collision: How can I calculate the effect of an object below 1 kg on another heavier object after colliding [closed]

I have a question on collision: 1. A light object (0.75 kg) is travel in velocity V m/s. 2. This object collide into another object which is about 9.5 times of its weight. 3. So, the question is ...
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### Ball collides with another. Find velocities [closed]

A ball moving at a velocity of 5.0 m/s east when it collided with an identical ball at rest. Both balls are the same mass. The first ball moved at 60 degrees north of east. The second went 30 ...
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### Classical particle in a box [closed]

I'm trying to work out some of the details for this system. A particle with mass $\mu$, initial velocity $v_0$ at $x_0$ and moving freely between two walls located at $\pm L/2$, with which it bounces ...
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### Collision of electron and proton of high energy [closed]

What will happen when proton and electron with high energy like in 100 TeV collide?
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### 2-D Elastic Collision [closed]

A bocce ball moving at 3.60 m/s strikes a second identical ball initially at rest in a perfectly elastic collision. The first ball moves off at a 36 degree angle from its original path and is ...
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### How did the scientists know two black holes collided 1.3 billion years ago?

I saw a TEDx talk the previous day about the LIGO experiment and in that video he said they are waiting for the day Jan 1st 2017 for the Ripple in Gravity caused by two black holes colliding each ...
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### Rigid bodies and inelastic collision

If two rigid bodies collide - how the collision can be inelastic? where the energy goes? If the energy transffered to heat, doesn't it contradict that the bodies are rigid?
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### Can collisions between particles in the canoncial ensemble be represented by a potential?

The professor in a statistical mechanics class said that in the canonical ensemble, you could represent interaction between particles as a potential in the partition function expression. But how about ...
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### Black Hole Collision [duplicate]

What would happen if two equally massive black holes directly collided at 5% the speed of light. I'm not talking about slowly orbiting each other for thousand of years. I mean one instant catastrophic ...
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### Calculating post-collision velocity [closed]

Consider two persons $p1$ and $p2$ of the same mass , such that they are together moving rightward with a velocity of $v/2$ Now person $p1$ pushes $p2$ in the left direction. According to newton's ...
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### Does inelastic collision mean the colliding particles have to necessarily stick?

In a case when particle 1 is moving vertically upwards and particle 2 if moving horizontally and they collide perfectly inelastically, why would the particles stick ? Since inelastic collision means ...
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### When a ball bounces on a wall at an angle, why does the angle of incidence equal angle of reflection?

When a ball is thrown to a wall without spin and bounces, supposing it's an elastic collision, why does the angle of incidence equal the angle "reflection" (relatively to the normal), why isn't it any ...
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### momentum and inelastic collisions

I have two bodies with mass of $A >B$ , these start from the endpoint of a straight line path and move towards each each other with a constant velocity $v$ , so that they collide for time $t$ , so ...
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### 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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### conservation of momentum? [closed]

At hyperphysics I got this image, with the same description in text as is in this image It says that when a massive particle (say $A$) moving with a velocity collides with an object having a ...
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### Off-center impulse equations [closed]

A rigid steel bar with mass $M$ is hit sideways (very close to its end) by a steel ball with mass $m$ and velocity $v$. What are the equations of motion after elastic impact and how about conservation ...
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### Ball Bounce Acceleration at the Point of Bounce [closed]

simple question but I wanted to confirm my approach of thinking about the problem. Question: A rubber ball is dropped from the fifth story of a building and free falls to the ground, after which ...
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### Why doesn't the 9th ball move in the break in the nine-ball pool game?

In the game of nine-ball pool, we break the rack like shown below: In the break, we hit the 1st ball with the cue ball. Many people familiar with pool games say that if the rack is constructed ...
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### Where does the energy go if a ball hits the ground WITHOUT bouncing? [duplicate]

so if a very un-bouncy object hits the floor and crashes into it rather than bouncing, where does most of the energy go? Does it simply turn into heat from friction? Or does it go into the Earth's ...
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### Will I die from a 50-foot fall? [closed]

Sorry if I didn't ask this in the right place, but... Will I die from a 50-foot fall? What are the chances of survival? I know this is more of a biology question or something, sorry :(
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### Acceleration of bodies

Whenever when there is collision or when there is continued movement during contact we assume there is only continued acceleration and no other type of motion. We use this assumption to find various ...
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### Electron positron collision producing mesons

An electron of an energy 9 GeV and a positron of energy E collide to produce a $B^0$ and anti-$B^0$ meson, each with a mass of 5.3 GeV. What is the minimum positron energy required to produce the $B^0$...
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### How do I handle elastic contacts in a simulation with friction [closed]

I'm trying to simulate a wheel as it hits the ground. Problem 1 Suppose a disc is dropped from a height. It has initial velocity of $-x,-y$ caused by throwing and gravity. It has no initial angular ...
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### Help with my bouncy ball lab (I know the factors just not how to approach them) [closed]

In my physics lab we need to determine the factors that account for the energy "loss" during a high bounce ball bounce. I know that energy is "lost" (not really) to heat, air resistance, and sound. ...