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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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
32 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
32 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
46 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 ...
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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 ...
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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 ...
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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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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
-3
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0answers
37 views

Finding the speed of a car [on hold]

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
41 views

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

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
40 views

Block over a Block Problem. [on hold]

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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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 ...
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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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4answers
102 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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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: ...
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3answers
67 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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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 ...
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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
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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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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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 ...
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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 ...
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0answers
15 views

Kinematics-Motion in one Dimension [closed]

A man is standing on top of a building 100m high. He throws 2 balls vertically, one at t=0 and the other after a time interval(less than 2s). The later ball is thrown at a velocity of half the first. ...
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0answers
43 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 ...
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0answers
17 views

Controlling the flow of powder from a container, based on grams selected [closed]

was wondering how you would control the flow of powder from a container (with a small cylindrical dispenser at the bottom). The container is filled with powder. As the container drains, less ...
3
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2answers
149 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 ...
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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 ...
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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 ...
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2answers
64 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 ...
2
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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
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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
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 ...
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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 ...
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3answers
100 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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4answers
49 views

Car Crash Scenario [closed]

Two vehicles travelling at 80mph in the same direction. Vehicles are directly behind each other. 12 meter distance between them. Front door of car in front rips of and hits the front window of the ...
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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 ...
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2answers
66 views

Kinematics Question AP Physics [closed]

A motorcycle officer hidden at an intersection observes a car driven by an oblivious driver who ignores a stop sign and continues through the intersection at constant speed. The police officer ...
0
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1answer
43 views

Can avg. Vel. be zero in uniformly accelerated straight line motion?

A particle moves in a straight line with constant acceleration. The average velocity of this particle in an interval is zero. According to me it may become possible when velocity of particle is in ...
1
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1answer
39 views

Nonzero acceleration is compatible with $d|\vec{v}|/dt=0$; why is the reverse not true?

It is possible to have change in magnitude of velocity w.r.t time to be zero and magnitude of acceleration to be non zero, $$\frac{d|\vec{v}|}{dt}=0 \quad \left| \frac{d\vec{v}}{dt} \right| \neq 0\, ...
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7answers
3k views

Flat throw vs 45 degree throw of a ball

Why does my sports coach tell me that when I'm fielding I should throw the baseball 'flat' to get the maximum distance? I thought from physics that you get the most distance from throwing at a 45 ...
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2answers
33 views

Distance traveled from displacement

I am currently reading a book called Physics for Scientists and Engineers by Serway. While reading the chapter about 2-dimensional kinematics, I asked myself a ...
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2answers
83 views

Convert an equation for acceleration into one for velocity

A sledge is pushed in a straight line. Assume surface is smooth. When the sledge is x distance away from the start the magnitude of its acceleration is given by $0.08e^{-4x}$ and is going in the same ...
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1answer
36 views

rolling a coin or a riding a bicycle [duplicate]

Why somebody riding a bicycle keeps balance and doesn't fall left or right, while is prone to falling when the bicycle stops. One force (to front) shouldn't affect in any way balance left/right. I ...
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1answer
69 views

Problem conserving 4-momentum at CoM frame in an inelastic collision [closed]

I am confused about the case where mass is not conserved in a collision (not due to relativistic factors). The center of momentum (CoM) frame is not the same before and after the collision. Let's ...
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2answers
65 views

Energy in the Relativistic COM Frame

I have been taught that in Classical Mechanics, the total energy of a system of two particles in the Centre of Mass Frame is given by $$ E_\mathrm{total} = \frac{1}{2}MV^2 + \frac{1}{2}\mu v_r^2 $$ ...
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1answer
33 views

the final velocity non-constant acceleration

I'm not sure if my problem was asked before, but if so, a simple link to the answer would be appreciated. Basically I've recently seen videos about spud cannons that use compressed air and it got me ...
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3answers
89 views

Difference between $|d{\bf r}|$ and $d|{\bf r}|$

What is the difference between $|d{\bf r}|$ and $d|{\bf r}|$ and why are both of them not always equal to each other? My question might seem stupid to some and will probably get downvoted but I have ...
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1answer
41 views

Explanation about friction force directions of two moving bodies in contact

can someone explain me why in this scenario (picture below) we have a friction force Ftr12 in the same direction as movement (left part of the picture, case 1 ) and how these directions of friction ...