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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16 views

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 ...
0
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1answer
103 views

Kinematics equations of motion find x position in 2D from height

I have a question and I thought of 2 possible ways to answer it however the resulting answers are different which means I must be doing something wrong in my calculations. All the below happens 2 ...
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4answers
91 views

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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1answer
22 views

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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3answers
44 views

Find constant acceleration with only initial speed and distance

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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1answer
34 views

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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1answer
30 views

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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1answer
47 views

How to predict the distance a ball rolls down a ramp between a certain time period [on hold]

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 ...
1
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1answer
341 views

Tangential and radial acceleration in projectile motion

I'm currently learing kinematics, specifically projectile motion and as an example in my textbook is a bullet fired at some angle. I understand the derivation of formulas to describe that motion and ...
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3answers
164 views

Animating an Acceleration Vector - Acceleration of object on a crested path in gravitational field

So I was reading in Chapter 3 of my textbook, Sears & Zemanksky's University Physics with Modern Physics by Young and Freedman, 13th Edition, and the discussion took us to a definition of the ...
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0answers
22 views

Mechanics - motion problem [on hold]

. A particle starting from rest accelerates at 2m/s2 for some time and then travels uniformly and passes a point 175m from the starting point 20m after start. The velocities of the particle at the ...
0
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2answers
55 views

Vertical Circular motion - Tension and velocity

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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0answers
29 views

about motion in 1D [on hold]

A body in one dimensional motion has zero speed at an instant. At that instant, it must have: (1)Zero velocity (2)Zero acceleration (3)Non-zero velocity (4)Non-zero acceleration ANS.(1) i want ...
7
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1answer
312 views

Is it possible to determine particles' velocities from their crossings on a ring?

2 particles are constrained to move in a ring. Both particles begin moving at $t=0$ from $p=0$, each particle moving in the opposite direction of the other. It is known that they are moving at ...
0
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0answers
40 views

River Boat Problem with a Twist [closed]

I am trying to solve the following river boat problem. A river of width $w$ is floating such that the stream velocity varies with $y$ as $$v_R=v_0(1+(\frac{\sqrt 3 - 1}{w})y)$$ where $y$ is ...
0
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2answers
35 views

Horizontal and vertical acceleration of a ball on a slope?

I understand that you resolve the components of the balls weight parallel and perpendicular to the slope in order to calculate the force due to gravity that actually acts down the slope. The ...
1
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1answer
327 views

Can there be force without motion?

I am confused. Can you have a force or tension without motion? Take for instance two robots with jet packs connected via a cord, each is flying in opposite directions. The tension of the cord is ...
-2
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1answer
22 views

Maximum horizontal speed and vertical speed interdependently [on hold]

I need to limit hspeed and vspeed taking direction in count, I know how to calculate the maximum speed as a whole, but not limiting that speed by setting the hspeed and the vspeed
0
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1answer
3k views

Finding the point of collision between two objects when acceleration is constant

$\newcommand{\accunit}{\mathrm{m}/\mathrm{s}^2}$ A coin is dropped 60.0m above the top of an elevator car. The coin is dropped just as the car begins to move upwards. The elevator first ...
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0answers
38 views

Finding the speed of a car [closed]

There is one car which got stolen which goes from the point $30$ in the negative sense of the "$x$" axe towards the point $0$ and has a constant speed of $160\text{ km/h}$. Another person notices ...
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2answers
5k views

Finding distance when the force is a function of time

I'm having trouble with this homework question A mysterious rocket-propelled object of mass 49.0 kg is initially at rest in the middle of the horizontal, frictionless surface of an ice-covered ...
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0answers
19 views

Kinematics Question: Velocity and Acceleration Polygons [closed]

I think I've been doing too many of these without much rest because I am stumped. The Curved slider mechanism is what is confusing me: Dimensions of a simple 2-bar linkage are given in the attached ...
0
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4answers
100 views

Does a flying bullet get KE from gravity?

A projectile P is shot horizontally at 9.8 m/s from a height of 4.9 m, considering no air friction, after a second it will have v = 9.8 m/s on the x-axis and v = -9.8 on the y-axis. Because of ...
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1answer
31 views

Problem: When does a constant velocity catch up to a certain acceleration? What is the maximum acceleration? [closed]

Physics noob here. Romeo is at x = 0 at t = 0 when he sees Juliet at x = 6m. (a) He begins to run towards her at v = 5m/s. She in turn begins to accelerate towards him at a = −2m/s2 . When ...
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2answers
41 views

A car honking it's horn, how long until the car hears the sound reflected? [closed]

A car is traveling with a constant speed v on a straight road which forms an angle α with nearby straight wall. When the car is at a distance l from the wall the driver presses the horn briefly. What ...
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0answers
26 views

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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2answers
211 views

Ball flying towards me - Newton's third law is violated?

I was trying to answer the question of the flying ball here on the basis of Newtons third law and Momentum conservation. Here is what I have tried. Lets take $m_1$ (the ball) hits $m_2$ (the man). ...
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votes
2answers
40 views

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 ...
1
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3answers
105 views

Motion of a rigid body: Why is motion only a compostition of two forms: rotation and Translation?

If you are in a 2-D space the motion of any rigrid body is composed of 2 different things, namely rotation and translation. If you are in 3-D space the motion of any rigrid body is also composed of 2 ...
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0answers
4 views

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 ...
5
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4answers
103 views

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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4answers
4k views

Why does the sun make me feel warm?

For a while I thought that the reason I felt warmth from the sun was because my skin was being hit by photons, but then I realized that photons also hit me when I take an X-ray, but I don't feel any ...
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7answers
848 views

Why is momentum conserved (or rather what makes an object carry on moving infinitely)?

I know this is an incredibly simple question, but I am trying to find a very simple explanation to this other than the simple logic that energy is conserved when two items impact and bounce off each ...
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1answer
34 views

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: ...
0
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3answers
68 views

What was the motivation behind the work formula?

Surely there must be a reason we decided to use this as a metric for mechanical energy.How was it developed and what made it more acceptable than other work formula candidates (Like force over time, ...
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3answers
526 views

Determine resultant velocity of an elastic particle-particle collision in 3d space

So I have two particles that have collided in 3 dimensional space. I want the particles to rebound off of each other in an elastic manner. How do I determine the resultant velocity vector if I know: ...
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0answers
38 views

It is possible to have a situiation in which $|\mathrm{d}v/\mathrm{d}t|$ is not zero but $\mathrm{d}|v|/\mathrm{d}t$ is? [closed]

Please explain the following in detail: It is possible to have a situation in which $\displaystyle\biggl\lvert\frac{\mathrm{d}\vec{v}}{\mathrm{d}t}\biggr\rvert\neq 0$ but ...
0
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1answer
27 views

Minimum turning circle of an accelerating spacecraft [on hold]

I think I've worked this out, but my maths/physics knowledge is far from perfect, so I'd love confirmation that it is correct. Basically, from $v =\omega r$ and $a_c = v^2 / r$ (where $\omega$ is ...
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0answers
16 views

Kinematics-Motion in 1 dimension [closed]

A motor car moving at 20m/s can not come to a stop in less than 3s while for a truck this time interval is 5s. On a highway the car is behind the truck both moving at 20m/s. The truck gives a signal ...
0
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0answers
44 views

Object pursuing exactly toward an uniformly moving object, with a twist

A friend of mine asked me about a problem he faced in an exam, but I happen to be rusty on this and can't seem to even understand it's implications, nevermind solve it. At $t=0$ an object A in ...
1
vote
2answers
66 views

Projectile motion of Golf ball- Can projection height be calculated just from initial velocity and travel time? [closed]

A Golf ball projected with a horizontal velocity of 30 meter per second and takes 4 second to reach the ground. Calculate the height the golf ball was projected from. Calculate the magnitude of ...
3
votes
2answers
150 views

Intepretation of area under velocity-time graph for a bouncing ball

A typical velocity-time graph for a bouncing ball is shown below. I understand that the ball starts from rest at $t=0$, then it accelerates downwards and hits the floor at time $t_1$. Between time ...
1
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2answers
242 views

Correct terminology for combined kinematic and dynamic state

The kinematic state is defined as the position and orientation in space. The dynamic state is defined as the associated velocities. What is the correct terminology for the combined kinematic and ...
2
votes
2answers
57 views

Does deceleration (or negative acceleration) feel like acceleration?

This may seem like a dumb question, but I'm having a hard time trying to intuit the answer. The question is in relation to Einstein's famous thought experiment which says that it is impossible for a ...
2
votes
3answers
169 views

Is there an intuitive explanation of the work formula?

Upon learning calculus, I decided it was time to derive all of classical mechanics to give myself a good understanding of physics. What I found was that, while trying to do so, I would need some ...
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1answer
182 views

Magnitude of the average velocity vector (not the average speed)

Thank you ahead of time for taking to look at this. For this following problem we were given an answer however I am almost positive the given answer is wrong. It doesn't even make sense. So here is ...
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1answer
47 views

Why do systems with a fixed gear-ratio still use gears?

From my understanding, there are two uses of a gearing system: to change the speed of output rotation (trading it with torque), and to change the axis of rotation. Now, in a car, for example, it is ...
0
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4answers
122 views

Why Do Objects move?

Let's imagine a block resting on horizontal table. When We apply a force which is greater than frictional force it moves. But why does this happen? Why can't friction withstand any force? As we know ...
0
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3answers
101 views

How can Kinetic energy formula and the Work formula be derived without assuming the other to be true?

After searching how to derive the formula for Kinetic energy, I found that most derivations required the use of the "work" formula. After searching how to derive the work formula for a bit, I found ...
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1answer
52 views

When will the velocity of a particle be perpendicular to it's initial velocity?

I am learning kinematics with vector analysis. I was given the position equation:$\mathbf{r} = 10t\hat{\mathtt{i}} + (20t-5t^2)\hat{\mathtt{j}}$. It asks me the time when the velocity of the particle ...