New answers tagged newtonian-mechanics
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Different Bernoulli equation from $F=dp/dt$
It is better to work with small elements and later take the limit.
$$\Delta p=\rho A_1\Delta x(v_2−v_1) \implies \frac{\Delta p}{\Delta t} = \rho A_1\frac{\Delta x}{\Delta t}(v_2−v_1)$$
The average ...
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Different Bernoulli equation from $F=dp/dt$
Thank you to whoever telepathically answered my question.
The answer can be found by asking yourself what happens if there is a piston pushing in the opposite direction on the volume of smaller cross ...
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Field of Inertial Forces
One way to arrive at what you suggest is to introduce the assumption that the phenomenon of inertia is mediated by a field.
In terms of newtonian mechanics you would then have two fields with a common ...
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Field of Inertial Forces
Inertial forces behave like any other force apart from not deriving from an interaction with other bodies. In particular, the inertial forces that depend on the position may define a vector field. ...
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The Work-Energy Theorem in Non-Inertial Frames: A Critical Analysis and Misconceptions
You can solve the problem by working in a non-inertial frame, but it is important to later calculate the velocities in the "ground" frame to determine the change in kinetic energy in this ...
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Do chargeable batteries break the third law of newton?
Assume that electrons are at rest inside a battery. Or if they move, they do so equally in all directions, so the net momentum is $0$. Also assume that they leave one battery terminal with some ...
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Newton's second law - local laws and non-local laws
I will give you two examples. First a local law and then a non-local law, explaining each with examples to make it much simpler.
Ok Local laws, such as Newton's second law for a car, tell you how fast ...
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Is the sectioning in method of sections, for truss analysis, arbitrary?
Yes. Since the sum of forces of any section of the trust must be zero, the net torque produced is going to be constant, moving from one location to another.
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Difference between Pulling a string and hanging a weight in an Atwood machine
If you are taking gravity to be 10m/s^2, there is no difference.
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Solving a coupled Pendulum using Eigenvalues method
You can rewrite your equations abstractly as:
$$
A\ddot X = BX\\
\begin{pmatrix}
m & 0 \\
0 & 2m
\end{pmatrix}\frac{d^2}{dt^2}\begin{pmatrix}
x \\
y
\end{pmatrix}=\begin{pmatrix}
-\frac{mg}{l}-...
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What can one say about the precision of the experiment if horizontal error-bars are wide and vertical error-bars are very small?
Yes, you can certainly state that "that there is high precision in the dependent variable but low in the slope due to wide horizontal error bars - poor precision - in measurement of the ...
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How to add components of velocity?
Where I am going wrong ?
You cannot add the vertical velocity components of the two parts of the string - your factor of $2$ is incorrect.
You are implicitly assuming that $\theta$ is constant - but ...
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How to add components of velocity?
$ \def \b {\mathbf}$
starting with Newton's second law
\begin{align*}
&\b M\,\ddot{\b{R}}=\b F+\b F_c
\end{align*}
where $~\b F~$ is external force and $~\b F_c~$ is constraint force
your case
\...
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Does car use more fuel when accelerating (for same delta) at higher speeds if resistance forces are constant?
As somebody has already pointed out
\begin{equation}
P=\vec{F}\cdot\vec{v},
\end{equation}
therefore, even assuming zero friction, if you fix the power of the engine, then the force (and the ...
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While lifting an object shouldn't a man apply a force equal to gravity but negative one?
Here, work done does not depend on the direction of action of gravitational force.
W=F.ds
We take W as negative when the displacement of the body is opposite to the applied force. We apply some force ...
3
votes
Accepted
Why rocket equation?
I think there is an abuse of notation. You should consider a differential increment. Then, the correct equation becomes:
$$ 0 = dp = m dv + v_e dm$$
$$ \int_{v_0}^v dv = -\int_{m_0}^m \frac{v_e}{m} dm$...
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I am confused in work-energy theorem, Why the ball doesn't go to the same height from which it fall down? (sorry if my grammer isn't correct)
Hey here in this question considering no dissipative forces present(friction, buoyancy,air resistance etc...)
On applying conservation of mechanical energy...
We get, mgh=mgh'+1/2mv²
See here I have ...
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I am confused in work-energy theorem, Why the ball doesn't go to the same height from which it fall down? (sorry if my grammer isn't correct)
Your ball would accelerate on its way down and have a velocity:
$ v1=v0+gt$ (that is g right? If no air drag is assumed, it should be. $v0,t$ respectively being the initial velocity and the time it ...
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I am confused in work-energy theorem, Why the ball doesn't go to the same height from which it fall down? (sorry if my grammer isn't correct)
I'm not sure what your question has to do with the work energy theorem, but the ball doesn’t reach the same height as its original height because it is still in motion (has kinetic energy) at the 1 m ...
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I am confused in work-energy theorem, Why the ball doesn't go to the same height from which it fall down? (sorry if my grammer isn't correct)
The key is to note that point C is a ramp, not a hill. The trajectory of the ball as it leaves the ramp is dependent very much on the angle of the ramp - a shallow ramp will result in a low, long ...
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I am confused in work-energy theorem, Why the ball doesn't go to the same height from which it fall down? (sorry if my grammer isn't correct)
Assuming no dissipation (friction, air drag), energy theorem tells you that the total mechanical energy is constant.
At the initial condition, the mechanical energy is completely gravitational ...
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My book states that contact force between two surface is equal to $\sqrt{N^2+F^2}$. where $N$ is the normal force and $F$ is the friction
It depends, what you call the friction force, the friction force is in the opposite direction of the movement, your hand moves in the direction. the magnitude of the friction force diminishes the ...
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Accepted
How do we solve polar coordinates related questions?
Hint.
$\vec{F} \times (\vec{r}\times \vec{p})=\vec{r}(\vec{F}\cdot\vec{p})-\vec{p}(\vec{F}\cdot \vec{r})$ by BAC-CAB rule, aka the vector triple product.
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How do we solve polar coordinates related questions?
You will find that hard to solve because the cross product is not well defined in spherical coordinates.
That means any cross product you come across in spherical coordinates you will want to convert ...
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When we push a block horizontally on a frictionless surface is their any normal force acting between our hand and block?
Adding to the other answers -
When the case is that only the block is on a frictionless surface - but the person is not (so the person can "push" the block without getting pushed backwards), ...
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Fundamental "definition" of momentum
When we say that massless particles have "momentum", are we even talking about the same thing as when we say that particles with mass have momentum?
The motion of the electric field in an EM ...
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What is the tension on a string with unbalanced forces on each side?
If an inextensible string is massless, and with unbalenced forces, it is accelerating infinitely fast. If it is inextensible, but not exactly massless with total mass $m$, then the acceleration at ...
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Only external forces can accelerate the center of mass of a system- paradox
Please explain where do I go wrong?
You are not dealing with rigid bodies.
Imagine a horizontal massless compressed spring which is attached to a box, which is on a horizontal frictionless surface, ...
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Understanding the double integral solution to Newtons second law?
We have
$$
v(t') =v(0)+ \int_0^{t'} a(t_1) dt_1=v(0)+\int_0^{t'}dt_1 F(t_1)/m.
$$
This follows from the fundamental theorem of calculus
$$
\frac{dv(t')}{dt'}= \frac{d}{dt'}\int_0^{t'} a(t_1) dt_1= a(...
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2
votes
Accepted
Only external forces can accelerate the center of mass of a system- paradox
BUT, work done by normal is zero as the point of application's displacement (the toes) is zero.
This is correct. Remember that there are two definitions of work. One is that work is force times ...
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Only external forces can accelerate the center of mass of a system- paradox
Please, don't mess things up.
Dynamics - some results
The second principle of dynamics reads, assuming constant mass of the system,
\begin{equation}
m \mathbf{a}_G = \mathbf{F}^{ext} \ .
\end{...
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Only external forces can accelerate the center of mass of a system- paradox
You get something wrong, it is not an internal force which makes the jump possible, but the normal force from the earth. but one uses like in the iceskating internal energy, so the jumping and the ...
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Only external forces can accelerate the center of mass of a system- paradox
As already pointed out by @Marius Ladergard Meyer 6 a force doesn’t need to do work to cause acceleration. Another example is the static friction force by the ground acting forward on a car wheel ...
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Accepted
When we push a block horizontally on a frictionless surface is their any normal force acting between our hand and block?
The red region I marked there the person hand is in contact with the
block I want to know if there is any normal force acting between the
person's hand and the block.
If the person applies a force $F$...
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When we push a block horizontally on a frictionless surface is their any normal force acting between our hand and block?
The force labeled $F$ is the normal force from the hands acting on the block.
The word "normal" simply means "perpendicular to the surface" in this context. The force $F$ is ...
- 92k
2
votes
Accepted
Help with Pulley Problem
The rope supporting $m_2$ is doubled up. Consider pulling $m_1$ all the way to the left as far as it will go, for rope length $L$. Now let $m_2$ fall as far as it can - since the rope is doubled up on ...
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Help with Pulley Problem
I thought acceleration and distance remains the same in a pulley system because the string is always the same length.
The string is always the same length, but the amount of string between $m_1$ and $...
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Will a radioactive ball conserve its angular velocity?
A sphere in vacuum ... should spin forever because of angular momentum conservation. However, assume that the sphere is made of radioactive material, or that its material is emitting radiation like ...
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About constant velocity linear motion with zero net force
I think your question is very interesting and important. Perhaps many people would misunderstand the difference between intertia motion and intertia coordinate/frame. As you mention, even though the ...
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How does gravitational potential energy work in a very large distance?
But when we change the direction of the asteroid slightly towards the planet, we create a situation where the mechanical energy becomes very large and negative
Why do you think this? The total ...
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How does gravitational potential energy work in a very large distance?
My answer
I understand that there is still some gravitational potential energy between the asteroid and the planet even when they are very far apart, but it is very close to zero.
So, the short ...
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How does gravitational potential energy work in a very large distance?
The gravitational potential energy is stored in the asteroid and planet system.
Turning the asteroid round makes absolutely no difference to the gravitational potential energy stored by the system as ...
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Car rolling away on an Inclined Plane with friction
This may help!
Take the example of a motorbike (2 wheels) and a car (4 wheels). At equal gear torque, both have the same acceleration. This implies that the no. of wheels does not affect the ...
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Why do rolling disc (coin) move in circular path?
$\vec{f_{1}}$ does not create a torque to cancel the weight's torque. Torque is $F\times r$, all torques have to be calculated w. respect to same point. If weight's torque was calculated w. respect to ...
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What really determines punching force?
As far as the physics is concerned, the real damage is caused by the impulsive force during the collision. If you deliver a punch with a huge velocity and the impact lasts for a short period of time, ...
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Friction & Normal Reaction
You should realize that there is no complete microscopic understanding of friction. And I am inclined to think that there is no universal answer to your question that would hold in general.
This being ...
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What really determines punching force?
as a Kinesiologist my non physicist take on this question relates to the neuromuscular connections that contribute to power. The question is of efficiency of force generation rather than force as an ...
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Expression for Potential energy of a hanging mass
Potential energy is never an absolute value - it is always measured relative to some base configuration or point that is assigned zero potential energy. And the location of this base point is ...
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Expression for Potential energy of a hanging mass
Because you need to choose a reference frame. It's not mandatory to choose the origin at the level of the ground, it's possible to choose the origin wherever you want but you must be consistent with ...
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Do conservative forces obey Newton's laws of motion? If we look closely, non-conservative forces like Friction etc follow 2nd law but Im confused
Newton's second law states that the net force acting on an object equals its change in momentum. The net force can be any combination of conservative and non-conservative forces.
The difference ...
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