All Questions
21,462 questions
0
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26
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Why do objects tend to flatten out around the axis of rotation?
The phenomena is shown here: https://starchild.gsfc.nasa.gov/docs/StarChild/teachers/spinning.html
I am trying to understand why this happens. I have already learned the concepts of angular momentum, ...
- 1
0
votes
1
answer
35
views
How can time taken to do Work be different?
Reading about Power today, I stumbled upon this question in my mind-
"How can the time taken to do a piece of work be different in 2 scenarios?" - when I came across, the example of '2 ...
- 3
0
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0
answers
16
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How does the initial angle of displacement influence the oscillatory damping rate experienced by a simple pendulum? [closed]
I suppose increasing the angle of displacement will cause a greater maximum speed achieved by the pendulum at the equilibrium position, and consequently damping. However, I do not find any research ...
0
votes
1
answer
25
views
How to show that angular velocity in 3D space is indeed a vector by using Feynman' method?
After reading this chapter of Feynman Lectures oh Physics: https://www.feynmanlectures.caltech.edu/I_20.html, inspired by Feynman's method in showing that torque is a vector, I decided to show that ...
- 421
2
votes
2
answers
75
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Intuitively, why is the quantity of kinetic energy conserved in a 1-dimensional elastic collision of rigid bodies? [closed]
Two blocks of masses and velocities $(m_1, \textbf{v}_{1,\:i})$ and $(m_2, \textbf{0})$ composed of identical material move towards each other on a frictionless plane in vacuum.
They collide. It is ...
- 21
2
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6
answers
1k
views
Why is Kinetic energy not an explicit function of acceleration?
A few days ago a high schooler asked me this question to which I couldn't give an answer.
His main question was that acceleration is also a property of a moving body so why is Kinetic energy which ...
- 8,476
-1
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0
answers
32
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Particle performing circular motion under influence of attractive force [closed]
A particle describes circular orbit under the influence of an attractive force directed towards point P on the circle. The magnitude of force can be written as kr^n (where k is some and r is the ...
-1
votes
0
answers
10
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What can we say about the dependence of resistive force on the velocity v of the bead? [closed]
Consider a fixed vertical circle. A large number of smooth, thin rods are fixed along the chords of the circle, all at different angles to the vertical. All the rods have their upper end at the ...
- 1
0
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0
answers
27
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Will a rocket rotate on any axis if there's a horizontal direction force acting below the center of mass of rocket?
Let a rocket is present in space very far away from any celestial body. There's a horizontal thrust acting on the rocket below the center of mass of the rocket, the small particles are launching ...
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2
answers
34
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What happens if a ball collides with a wall that provides a perfect rebound and the wall disappears after half the contact time?
I would like to pose a question that currently sparks my curiosity, and I would appreciate your help in answering it.
Imagine a ball colliding with a wall that provides a perfect rebound for the ball. ...
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0
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1
answer
42
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Why will mass $m$ stop moving in this question?
The question says:
Mass $m$ carrying a charge $q$ is suspended from a string and placed in a uniform horizontal electric field of intensity $E$. Find the angle between the string and the vertical in ...
- 33
3
votes
3
answers
213
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Relations between the strong form of Newton's 3rd law and conservation of angular momentum?
How does using the strong form of Newton's 3rd law
Forces between particles come in action/reaction pairs, and these forces are directed along the line of separation between the two particles.
Gives ...
- 105
1
vote
1
answer
40
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Why do we include both local and temporal acceleration in fluid mechanics but only consider temporal acceleration in solid-body mechanics?
I am a beginner in physics, and I was studying fluid mechanics, specifically Newton's second law, when I was surprised to find that the expression for acceleration was composed of both local and ...
- 11
-1
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2
answers
32
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Influence of wind on an aircraft’s ground speed
I wonder if you can help settle this argument.
An aircraft is flying in circles, with a constant angle of bank, at a constant airspeed of 80kts, at a constant altitude, in a steady 20kt wind from the ...
-2
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0
answers
25
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A rope with length $L$ and mass density $ρ$ is suspended vertically from one end. Find the tension as a function of height along the rope [closed]
A rope with length $L$ and mass density per unit length $ρ$ is suspended vertically from one end. Find the tension as a function of height along the rope
I just don’t understand the way the functions ...
0
votes
2
answers
69
views
Does every object in space have a weight (disregarding negligible external forces)?
Defining weight as the "gravitational force acting on an object", and disregarding the minimal impact that gravity has on objects considered to be 'gravitationally unbound', do all objects ...
-2
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0
answers
76
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Has low pressure been generated in the open space of this device?
A represents the left and right speakers, B represents the left and right baffles, C represents the rectangular holes on the left and right baffles through which the sound waves from the speakers can ...
- 2,165
0
votes
1
answer
38
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Finding the accelerations and tension of a pully wedge system [closed]
According to the figure below, a wooden cuboid A of mass "M" is suspended to a horizontal fixed straight inextensible string which passes through 2 smooth rings which are attached to the ...
0
votes
0
answers
47
views
How to calculate torque and force at center of mass of a tilted block due to gravity? [closed]
Please how to determine torque and force at center of mass of a tilted block with uniform density, width $w$ and mass $m$ making an angle $\theta$ with ground?
I have an idea:
If the block is resting ...
- 21
1
vote
1
answer
59
views
Gravitation satellite orbiting earth
In circular orbit as angular momentum is conserved so we can write $v$ is inversely proportional to $r$ but by equating gravitational force and centripetal force we get that v is inversely ...
0
votes
3
answers
85
views
Is the $\Sigma$ in Newton's second law the sum operator or an "arbitrary" notation?
In high school physics, I often saw the equation: $$\Sigma\vec{F}=m\vec{a}$$At the time, I understood it as "the net force is the sum of all forces acting on a body." Now that I’m studying ...
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2
votes
0
answers
41
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Why initial conditions matter while interfering with ongoing SHM of a mass with electric charge and placed in electric field?
The question is related to the situation:
A body of mass M and charge q is connected to a spring of spring constant k. It is oscillating along x-direction about its equilibrium position, taken to be ...
- 21
-10
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0
answers
63
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What is the fundamental difference of the old Aether concept with that of today's concepts of dark matter and dark energy? [closed]
If you strip from Aether the old falsely believed property that it interacts directly with light then will you not end up with Dark Matter and and Dark Energy concepts and in general the dark sector?
- 4,376
0
votes
0
answers
12
views
Component of force [duplicate]
If I have a wedge at angle $\theta$ and a small object of mass $m$ on it I can break the gravitational force into two components $mg\sin\theta$ and $mg\cos\theta$ and block will slide down because of $...
- 13
1
vote
1
answer
108
views
Why does that screw-propelled vehicle steers opposite to common sense?
Watching videos of screw-propelled vehicles, I came across this one, where at some point (2:15 to 2:40) there's one weird steering/yaw reversal:
While driving forward in a swamp, thrust comes from ...
- 483
3
votes
4
answers
198
views
What is the relation between bicycle rear wheel path and front wheel path?
I'm not a physicist, more of a mathematician. I want to solve a puzzle which apparently requires the physical knowledge of how front wheel path (F) and rear wheel path (R) of one and the same bicycle ...
- 41
2
votes
5
answers
503
views
Motion of fragments
This is a general question regarding the motion of fragments of a single particle at rest, with no external force acting on it.
Say I have a (point like) body of mass $m$, situated at the origin of my ...
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-2
votes
0
answers
45
views
Where am I making a mistake? [closed]
In solution to this question we say $dW/dt=$power that is constant so $F.v$ is constant so with time when velocity increase force must decrease.
But the formula $F.v$ is itself valid in cases of ...
- 27
0
votes
2
answers
55
views
How does the steering wheel return to the centre after turning (and letting go)? What forces are causing the self centreing torque?
https://www.youtube.com/watch?v=wLbs8kBXgrw
This is a very interesting phenomenon to me as it is purely physical and not a result of hydraulics or whatever.
I watched this video (please watch it for ...
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-3
votes
2
answers
64
views
Work-energy Confusion [closed]
When a system is losing energy and do some work on an object to make it gain Kinetic energy, then the energy lost by the external system could have been stored in what form(s)?
Refer to this system: ...
- 167
-4
votes
0
answers
23
views
Newton's law of motion without friction [closed]
To disc of masses M1 and M2 are connected by a spring force constant K the lower disc of M2 lies on a table and upper disc is vertically above it what vertical force f should be applied to the upper ...
-1
votes
1
answer
28
views
Inconsistent result when finding the minimum speed to reach the highest point of a circular road [closed]
A car moves from $A$ to reach the highest point $B$ of a vertical circular road. Find the minum speed of the car at $A$. Ignore all frictions.
Using conservation of energy
\begin{align*}
mgh_A+\tfrac{...
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1
vote
1
answer
133
views
Trouble with the concept of external force on a system
In the diagram above, there is no frictional force on $m_1$, the rope and the pulley are massless. There is earth gravity.
We find that the horizontal component of the acceleration of the center of ...
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2
votes
1
answer
68
views
What is the maximum displacement at which a series of blocks can be displaced vertically?
This is a really simple question that I've been thinking. The statement is as following:
Consider you have a series of blocks, each of length $l$, width $w$, height $h$, and mass $m$ wich is evenly ...
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-2
votes
0
answers
34
views
Find angular momentum of the following system [closed]
I want to know the angular momentum of the system about the point O. All three are rods of mass m and length l. Rod1 is moving linearly while axis of rod 2 is fixed on rod 1 and rod 3 on rod 2.[
-2
votes
0
answers
26
views
Centripetal acceleration and gravity acceleration [closed]
Can you explain, The combined effect the centripetal and gravity acceleration.
- 1
0
votes
0
answers
45
views
Particle-mesh method & energy conservation [closed]
Disclaimer: I'm a complete novice when it comes to computational physics but I want to learn more. As a starting point, I wanted to implement the particle-mesh method following Hockney's textbook ...
- 1
0
votes
0
answers
30
views
Why kinetic energy is equal to work done? [duplicate]
My textbook says that work done is equal to the change in kinetic energy. But is there a proof for it?
( not the equation where you say
W= ½mv²- ½mu². There you substitute W with Kinetic energy. Ineed ...
- 23
0
votes
0
answers
42
views
Dynamics of a drifting car
Assuming we know the properties of a moving car (static friction, dynamic friction, force applied by wheels, velocity, heading, mass, wheel rotation, etc.), when does the car drift and what are the ...
- 1
0
votes
1
answer
43
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Difference between torque about point and torque about axis [duplicate]
What is the difference between torque about axis and a point? Why do we calculate torque about axis sometimes and torque about point sometimes? How we can identify when to calculate torque about a ...
- 3
0
votes
2
answers
48
views
How to determine if there is frictional force?
Imagine two vertical wooden boards clamping a small object. Assume that the left board is smooth, and the friction from the right board is enough to prevent the object from falling due to gravity. Now,...
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2
votes
5
answers
204
views
Is there a principle that determines the tension in this system?
I encountered a doubt while solving this question:
My try. (I have not shown friction force direction but its leftward for all three blocks.)
I have solved this question and have got all correct ...
- 29
1
vote
1
answer
67
views
Forces between two like charges and Newton's third law
Two like charges, $q_1$ and $q_2$, are placed at a certain distance from each other. Charge $q_1$ repels charge $q_2$ with a force $F$ due to electric field of $q_1$, and according to Newton's third ...
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0
votes
2
answers
58
views
Is the efficiency of a balanced lever 100 percent?
I was kicking around some lever concepts, actual mechanical advantage and ideal mechanical advantage.
Oftentimes we say that ideal mechanical advantage for a class I lever is
$$IMA = \frac{d_E}{d_R}$$
...
- 919
0
votes
2
answers
36
views
Why is friction required to rotate a non-ideal pulley-string system?
As the title says, why does a pulley require friction to rotate?
I understand that, due to the mass of the pulley, the string will have different tensions on either side. [Assuming there are blocks of ...
0
votes
1
answer
43
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What is the base of defining eccentricity like this?
In an Introduction to Modern Astrophysics, the author first derived the Laplace-Runge-Lenz vector, and then used the vector to derive the equation of orbit ($\mu$ is reduced mass, $\mu = \frac{m_1m_2}{...
- 453
0
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0
answers
31
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Equilibrium of a lever with non-negligible mass
How does a lever with non-negligible mass behave? How should I go about calculating the torque so that I can write the equilibrium condition?
My idea was to use an integral, that is, if the origin $\...
- 201
1
vote
2
answers
68
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Doubt with Heat and Potential Energy. (Warning: Many Assumptions) [closed]
I had a question in my Textbook which reads as follows,
Before that, we have to assume that the flowing water is ideal.
So, here we have to equate Change in Potential Energy to Heat Energy/Internal ...
6
votes
4
answers
587
views
Limits of the integral for the calculation of work
To calculate the total displacement for a time dependent velocity, one can start from an infinitesimal displacement and integrate as follows
$$dx=vdt$$
$$ \int_{x_i}^{x_f}dx= \int_{t_i}^{t_f}vdt $$
$$ ...
- 2,410
0
votes
3
answers
238
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Pivoting rod analyzed about a rotating axis
When solving a classic rotational dynamics problem — a uniform rod of length $L$ and mass $m$, pivoted at one end by frictionless pin and released from rest in the horizontal position rotates under ...
- 39