# Tag Info

### What happens if a slow train hits you?

You can think of this in terms of falling from a height of say one foot (e.g accidently rolling off your bed). You hit the surface with a low velocity and it is survivable (but not always) despite the ...
• 1,858

### What happens if a slow train hits you?

One of the joys of physics is that you can often reframe the problem. In your problem, you have a moving cube and a person standing still. Thus you are thinking in the frame of the person. But you ...
• 46.6k

### What happens if a slow train hits you?

for a slow collision, the inherent springiness or elasticity of your body will provide enough time in the course of the collision to bring you up to speed and to slow down the big cube by some ...
• 92.1k
1 vote

### Elastic collision between 2 particles in 2D

Try to square your solutions for $v_0$ and $u_1$, you'll get a simplification by summing them ; then you'll be able to express $u_1$ and $u_2$ as a function of $v_0$ using this new equation and the ...
• 149
1 vote

### Why does striking two balls of equal mass and equal magnitude of velocity turn the system to rest?

If in an inelastic collision particle A has a velocity magnitude greater than that of particle B, then the velocity of the combined particle will be non zero and in the direction of A before the ...
• 1,858

### Prove coefficient of of restiution is 1 for perfectly elastic collisions

starting with Newton equation immediately after the collision \begin{align*} &m_1\,\frac{d\mathbf v}{dt}= -F_c\,\mathbf n\quad\Rightarrow\\ &m_1\,\int_{\mathbf u_1}^{\mathbf v_1}=-\int F_c\,\...
• 11.7k

### Prove coefficient of of restiution is 1 for perfectly elastic collisions

If, in a collision between two spheres, the coefficient of restitution is unity, then for the velocity components parallel to the line $O_AO_B$ joining the spheres' centres at the collision... ...
• 35.4k

### Where does a body get its energy to heat up when falling from height $h$?

A body that is at some height $h$ has some potential energy due to Earth's gravitational field. When it is dropped, then it will be converted into kinetic energy. Let us say that when there is no air ...

### Where does a body get its energy to heat up when falling from height $h$?

When a body falls from height part of its energy is lost due to friction with air. Note that the temperature is only a measure of the kinetic energy of the molecules of an object. Due to the effect of ...

### Acting forces on a curve ball (billiards)

The poster is correct that the ball would normally veer to the right with the left-side hit causing clockwise rotation. This is not a regular hit on ball on the left side of cue ball, however. This ...

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

I came across something similiar like this which might help you with your question in this book: Thinking Physics practical lessons in critical thinking by L e w i s C a r r o l l E p s t e i n. You ...
Accepted

### Is the collision in LHC quantum mechanically so we cannot predict the trajectory?

The particles in the accelerator are described within the framework of quantum field theory, a relativistic quantum theory that treats particles as excitations of interacting operator-valued fields. ...
• 1,529
1 vote

### Can't understand inelastic collisions

Kinetic energy, during a collision, is lost, for eg., as sound energy. If there is no dissipation of energy in any manner (sound/heat/light) we call it an elastic collision, and then you can conserve ...
• 720

### Does acceleration or deceleration affect the strength of impact if velocity is the same?

@Cort Ammon, Also the Accelerometers in the SRS are directional and have tiny floating masses. The slowing Car has a preload on the forward crash sensor, towards activation. Where the Acceleration Car ...
Accepted

### Does acceleration or deceleration affect the strength of impact if velocity is the same?

The acceleration will not matter. What will matter is the momentum of the car, which is entirely defined by velocity, not acceleration, and energy of the car, which is entirely defined by the ...
• 46.6k
1 vote
Accepted

### Can we figure out normal force acting on a body after it has collided?

Yes, you need to know the coefficient of restitution to find the momentum that is transferred from $m_1$ to $m_2$ during the collision. To find the average normal force between the bodies during the ...
• 50.5k

### Can't understand inelastic collisions

In inelastic collisions, the kinetic energy of the system is not conserved however momentum is still conserved. How is this possible? Think of them compressing a mutual one-way sticky spring (that ...
• 251

### Can't understand inelastic collisions

If the energy is conserved, we have $$m_1u_1^2+m_2u_2^2-m_1v_1^2-m_2v_2^2=0.\tag{1}$$ Your equation: $$m_1u_1+m_2u_2=m_1v_1+m_2v_2.\tag{2}$$ Now taking the square: \begin{align} (m_1u_1+m_2u_2)^2&=...

### Can we figure out normal force acting on a body after it has collided?

A rigid body generates enough force to keep from being deformed. If $m_1$ and $m_2$ are pressed together, they press back just hard enough to keep from digging into each other. If you stop pressing, ...
• 37.9k
An example in a very different context is in atomic and molecular collisions with surfaces. If I shoot an atom at a surface with some kinetic energy $T_i$ and it bounces off the surface with a kinetic ...