# Tagged Questions

The description of the movement of bodies by their position, velocity, acceleration (and possibly higher time derivatives, such as, jerk) without concern for the underlying dynamics/forces/causes.

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### Half-atwood machine with accelerating pulley

This is a follow-up to my previous question, in which I am now trying to calculate the acceleration of the cart (as before, the block surfaces are frictionless). The mass $m_2$ is attached to $M$ via ...
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### What is the physical significance of Rapidity in Relativistic kinematics?

Recently I have came across a new term called rapidity in relativistic kinematics. We are using it in relativistic kinematics due to its additivity whereas velocity is not a additive quantity in ...
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### Pulley system on a frictionless cart

Let's say you have a pulley set up as below on a cart, with a massless pulley and string. The mass hanging off the side is attached via a rail, and all surfaces & pulley are frictionless except ...
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### How can we apply Newtons laws, or kinematics to solve a problem like this one?

Problem: Two objects with masses 5.00 kg and 2.00 kg hang .600 m above the floor from the ends of a cord 6.00 m long passing over a frictionless pulley. Both objects start from rest. Find the maximum ...
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### What is the acceleration at the top most point of a ball’s journey vertically upward?

When i shoot a ball vertically upward, it’s velocity is decreasing. So there is acceleration. -9.8m/s^2. I’ve read that at the top most point, the acceleration is STILL 9.8 m/s^2 where v=0 . The ...
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### Velocity required for a car on a a frictionless banked surface

My textbook has clearly explained and derived a velocity that is required for a car to navigate a turn on a frictionless banked surface. I have understood it too. My doubt is about what happens when ...
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### Why the point right below the center of a rolling ball on the ball has zero instantaneous velocity [duplicate]

Suppose there is a snooker ball rolling on a table. The velocity of the center of the ball is Rω and its direction is horizontally right. I don't understand why the point right below the center on the ...
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### Problem regarding bullet penetration [closed]

Which property remains constant when we say that bullets are penetrating the wall? I mean is the resistive force always constant for a given wall (assumed stationary and immovable) irrespective of the ...
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### Disk Free falling in magnetic field

A circular metal plate starts falling from rest in a region of uniform magnetic field "B". B is parallel to the plane of plate and to the surface of earth(refer to diagram).The plate has mass "M" ...
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### Value of $g$ in projectile problems

A cannon has a muzzle speed velocity Vo of 60.0m/s, at what angle theta should it be aimed to strike a distance 320 meters away. Ignore air resistance So I get how to set this up but I am confused ...
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### Does $v^2=v_0^2-2gh$ work if the positive axis is up and the initial velocity is down?

In the situation where the positive axis is up, the acceleration due to gravity is $g$, and the velocity is represented by the equation $v^2=v_0^2 - 2gh$. This works great if the initial velocity is ...
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### Invariant mass spectrum to a transverse momentum distribution

For the decay of the Higgs boson in 2 photons having the following invariant mass formula: $$M = 2E_{1}E_{2}(1 - \cos \theta)$$ How can I go from an invariant mass spectrum distribution to a ...
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### Is this an acceptable approach to solving the following problem? [closed]

Why does my approach not work for the following problem? PROBLEM A man stands on the roof of a building of height $14.6\,\mathrm{m}$ and throws a rock with a velocity of magnitude $32.1\,\mathrm{m/s}$...
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### if a body is stopped by means other than friction, where does energy go?

Suppose we have an object in space. say gravity is negligible, and the thing has a rocket on both sides. the thing fires one rocket for, say, 5 seconds. now it's moving. The object has kinetic energy. ...
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### What information do I need to find to solve this kinematics problem? [closed]

The question is this: As you look out of your dorm window, a flower pot suddenly falls past. The pot is visible for a time $t$, and the vertical length of your window is $L_w$. Take down to be the ...
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### What is the intuitive meaning of $Q^2$?

In particle physics, $-Q^2$ is defined by the four momentum transfer squared: $$Q^2 = -(p_i - p_f)^2 = (\vec{p}_i-\vec{p}_f)^2-(E_i-E_f)^2$$ For elastic scattering, the meaning of $Q^2$ is clear - it ...
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### Why is there a universal speed limit?

I am looking for an answer that does not rely on Special or General Relativity -and without recourse to the fact that the speed of light is frame invariant. Is there another way of showing this ...
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### Proving a kinematics problem

I recently read in a book that the distance covered by an object projected vertically upwards in the last second of the upward motion is a constant independent of initial velocity.I tried to prove it ...
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### Find constant acceleration with only initial speed and distance [closed]

Given the problem: "A car moving initially at 50 mi/h begins decelerating at a constant rate 60 ft short of a stoplight. If the car comes to a stop right at the light, what is the magnitude of its ...
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### Does motion with constant proper acceleration, in a flat region, necessarily mean straight hyperbolic motion?

Is motion of a participant with constant proper acceleration, in a flat region, necessarily straight, hyperbolic motion (with respect to members of any inertial system, in that region)? Or is for ...
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### Lifting a block or sliding a block- Which will consume more energy?

A box with mass m units resting on a table with smooth surface (slightly oily). A to B : d units Action 1 : Slide the box from Point A to B. Action 2 : Lift the box from A to B in an arc fashion. ...
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### How to predict the distance a ball rolls down a ramp between a certain time period [closed]

At t=0 a ball, initially at rest, starts to roll down a ramp with constant acceleration. You notice it moves 1 foot between t=0 seconds and t = 1 second. How far does it move between t = 1 second and ...
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### Vertical Circular motion - Tension and velocity [duplicate]

I read through the question Minimum velocity of the particle at the highest point which is quite similar to my questions. But I still have some doubts in the answers - "The particle will complete ...
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### Angular Speed and Normal Speed

The instantaneous speed of a point along a circular path is given by $v=\omega r$, where $\omega = \frac{\Delta \theta}{\Delta t}$, $s=\Delta \theta r$, and $v=\frac{s}{t}$. However, isn’t the ...
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### Block over a Block Problem. [closed]

This a block placed on block problem. In this problem, A block with mass 40 kg in placed on a block of 60kg which lies on a frictionless surface. The coefficient of friction between 40kg mass and 60kg ...
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### Water flow in salt solutions contemporary exposed to an electrical and constant magnetic field

When a permanent magnet is held motionless close to a salt solution which already has been exposed to an electrical field a flow in the water will be induced and can be detected by applying some ...
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### How can we explain the difference in change of kinetic energy, due to different frames of reference?

Imagine a ball ($m= 1\,{\rm kg}$) moving at a velocity $2\,{\rm m}/{\rm s}$ towards a wall. When it hits the wall, it suddenly stops, thereby liberating all its ${\rm KE}$ as heat. Here, the initial ...
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### How can I estimate CO2 emissions for a vehicle travel distance

How can I properly estimate CO2 emissions for a given travel distance (of a private vehicle)? I found the following formula, but I'm not sure that it's correct: ...