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Potential Energy, Kinetic Energy, velocity, question?

A man standing a certain height above the ground throws a rock straight up with an initial velocity of 10 m/s. A few moments later, the rock hits the ground with a kinetic energy of 450 J. If the man ...
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0answers
6 views

What is the minimum velocity a toy car has to travel in order to survive going through a loop of radius 0.2 meters?

I tried height = 2 * radius = 2 * .2 m = .4 m. Potential energy = mgh. Kinetic Energy = $\frac{1}{2}mv^2 = mgh$ Then $\frac{1}{2}v^2 = gh$ $v = \sqrt(2gh) = 2.8 m/s$ The correct answer is 2 ...
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2answers
15 views

Ratio of Kinetic Energy Concerted to Internal Energy

I need help with this question: Consider four identical cars. Two of them collide head-on when both are traveling at 34 m/s. The other two collide head on when both are traveling at 25 m/s. What ...
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1answer
15 views

Directly calculate electric potential due to a spherical volume charge

Q: Say we have a uniformly charged sphere with radius R, total charge Q. Now we need to find out the electric potential inside the sphere, at a distance r from the centre. I understand that we can do ...
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3answers
30 views

Given Force in vector form, how do I find work done?

A force of $F=\hat i+2\hat j-3\hat k$ is applied to a particle that moves 10 meters in the direction of $\hat i+\hat j$. How much work is done?
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0answers
19 views

equilibrium pulley system [duplicate]

the question asks what mass i need for m1 to be in static equilibrium while m2 is given as 60kg. im not sure first of all if that means the two masses have to be equal in length balanced. secondly, ...
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1answer
49 views

How do I find the angle given the mass, the acceleration and the force acted on a body?

My Issue I have the mass, the horizontal acceleration and a force that acts on a body. The force forms an angle $\alpha$ of unknown degrees with the x-axis. I would like to know how I can find the ...
-2
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0answers
53 views

mass needed for equilibrium in pulley system [on hold]

Question says: For what m1 will the illustrated pulley system be in static equilibrium if m2 = 60 kg? ive tried equating the changes in length where change in x1 is equal to twice the change in x2 in ...
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1answer
29 views

Force of impact of a projectile [on hold]

I need to calculate the force of impact of a projectile on a target . The projectile has been fired at an initial velocity $U$ and an angle of departure $X$. The projectile is hitting the target at an ...
1
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2answers
42 views

How do I find the horizontal acceleration of a body given its mass and the force that acts on it? [on hold]

My Issue I have the mass of a body and the force that is acted on a body. I am trying to calculate the horizontal acceleration and to understand how the horizontal acceleration is connected with the ...
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0answers
14 views
0
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0answers
22 views

Show that the radius of the equipotential surface between +3C and -1C charges is $\frac{3}{8}$m [on hold]

This question concerns two point charges of values +3$C$ and −1$C$. The two charges are fixed in position with a separation of exactly 1 metre. Consider the positive charge to be placed at the origin ...
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2answers
15 views

Finding the torque on a dipole affected by electric field

A $H_2$ molecule with charges $\pm p$ separated by $d=10^{-10}$m and masses $1.66\times 10^{-27}$kg is put into an electric field with uniform strength $E$, making an angle $\theta$ with this field. ...
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1answer
27 views

Pulling a bar through a magnetic field

This is a question on magnetic flux and induced voltage. I believe that this problem's answer key is incorrect, and I want to determine whether my opinion is sound. I also want to explore one ...
1
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1answer
19 views

2D square lattice, nearest neighbor and next-nearest connected by springs

For my field theory class I am trying to build the Lagrangian for the following system. Consider a 2D square lattice where the nearest and next-nearest neighbor interactions are modeled by springs ...
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1answer
25 views

Finding the current and voltage in a circuit with DC sources

I know that in a circuit with DC sources a capacitor(steady state) can be replaced with an open circuit and an inductor(steady state) can be replaced with a short circuit. My understanding is that ...
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0answers
24 views

Finding force acting on an object using work energy theorem [on hold]

An object of mass 5kg passes through the origin at $t=0$. $x$-component of velocity is 4 and $y$-component is -3. At a later time $t=3$ the object is located at $x=9$ and $y=5$. What is the force ...
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1answer
49 views

Using differentials to optimize a function [on hold]

I've read in a paper by Tevian Dray an alternative way to solve optimization problems manipulating "differentials". Here is an example of how it works (next I quote the paper). Consider the ...
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1answer
56 views

Effect of a rotating disk on a grandfather clock

The question is as follows: A grandfather clock is placed on a rotating disk. Given the disk rotates once every minute, how long does it take for the clock to be one second out? Am I correct in ...
1
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0answers
30 views

Calculation of angular acceleration [on hold]

Hi I am doing a physics question and it's like this: Two identical blocks, each of mass M, are connected by a massless string over a pulley of radius R and rotational inertia I . When the system is ...
0
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0answers
18 views

Calculating the entropy of a monatomic ideal gas

I am looking at the start of the consider how to calculate the entropy of a monatomic ideal gas. We need to determine the number of microstates in $E \leq \mathcal{H}(\Gamma) \leq E+\Delta$. The ...
1
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1answer
43 views

How do i correctly go from a two variable function to a function of difference?

I would like to know how I can go from a two argument function $g(x_1,x_2)$ formally correct to a function of the difference of the parameters $g(x_1-x_2)=g(x)$ this seems to involve integration over ...
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0answers
14 views

Equivalent force–couple system STATICS Meriam 6th exer. 2/71 [on hold]

I need a bit of help to clarify what I couldn't see here. 2/71 The system consisting of the bar OA, two identical pulleys, and a section of thin tape is subjected to the two 180-N tensile ...
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0answers
27 views

When does a balloon burst? [on hold]

I'm working on a project and I need to know something. and that's : When does a balloon burst? I mean, does it have any relation to its internal pressure or its volume? for example can we say a volume ...
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0answers
13 views

Find the length of time for which the direction of motion is between 20 degree above and below the horizontal [on hold]

A particle is projected with speed $65\, m s^{−1}$ from a point on horizontal ground, in a direction making an angle of $\alpha$ above the horizontal. The particle reaches the ground again after $12\, ...
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3answers
52 views

What is meant by a “sodium line”?

What speed should a galaxy move with respect to us so that the sodium line at $589.0\ \mathrm{nm}$ is observed at $589.6\ \mathrm{nm}$? In the above question what's meant by a sodium line? The ...
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0answers
24 views

Acceleration of an incompressible fluid along a conical pipe [on hold]

I've been reading Theory of Flight by Richard von Mises and early on I came across this problem. The full text of the problem is as follows: "Show that along a conical pipe the acceleration of an ...
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2answers
28 views

Pendulum point in polar coordinates for Lagrangian

So I'm really stumped with this. I have a particle in a cone, like pictured. The particle orbits the z axis on the dotted line for $r$. So knowing that $\alpha$ and $r$ remain constant in this ...
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2answers
20 views

Radiometric dating calculation [on hold]

If a sample of zircon initially contains no Lead, find an expression for the ratio $$\frac{N_U}{N_{Pb}}$$ as a function of time? How do I do simplifications from this? Do I just go: ...
-1
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0answers
15 views

Force and tension on a set of ropes [on hold]

I'm having trouble figuring out what to do after getting the force acting on lines AB and BC (I'm getting about 117N), how do I figure out the forces on BC, BD, and CE? Since the system is ...
0
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1answer
20 views

How to calculate error of this powers? [on hold]

How to find the error of this? 3*{10^ ([m sun - m c]/2.5)} If m sun or the apparent magnitude of the sun=-26.7and doesn't identify its error. And m c =23.79+- 0.26 My work is: For m sun-m c= -50.49 ...
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1answer
27 views

Conserved current in a complex relativistic scalar field

For my field theory class I have the following Lagrangian density $$\mathscr{L}=\frac{1}{2}\eta^{\mu\nu}\partial_\mu\phi^*\partial_\nu\phi-\frac{1}{2}m^2\phi^*\phi$$ Where $\eta^{\mu\nu}$ is the ...
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votes
1answer
45 views

How does the equation $1/I = r/E +R/E$ relate to $ y=mx+c$? [duplicate]

I have a graph of $1/$current against resistance, which is a straight line of positive gradient. I know that the gradient represents $1/V$ but I can't work out how the equation $1/I= r/E + R/E$ ...
1
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0answers
31 views

Potential difference between Earth's surface and 2 meters above

Assuming Earth is a charged sphere of radius $R = 6400.10^3 m$ with uniform surface charge density $\sigma = -10^{-9} C.m^{-2}$ and with $\epsilon_0 = 8.85.10^{-12}F.m^{-1}$ I find that ...
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3answers
43 views

Tension Problem: Finding an angle when only given the tension in two ropes [on hold]

A crate is hanging from a rope which is attached to a metal ring through which a second rope runs, as shown to the right. What is the angle $\theta$ if the tension in rope 1 is $1.19$ times the ...
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2answers
35 views

Calculating the time constant for charging a capacitor in a circuit [on hold]

Problem: Calculate the time constant for charging the capacitor in the shown circuit. What is the maximal charge on the capacitor? Attempt at a solution: Let current $I_1$ flow from the emf ...
-2
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0answers
20 views

What would be the formula for the time to impact of an object travelling at a constant velocity? [on hold]

What would be the formula for the impact time of an object? Assuming that the object is falling at a constant velocity, for example, the object is falling at 5 m/s, and is 50 meters away from the ...
3
votes
1answer
30 views

Potential energies of charges and spring

I wonder if someone could sanity check this very simple calculation. Consider a pair of charges $+q$ at rest separated by a spring of length $d$ and stiffness $k$. The spring provides the force that ...
-2
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0answers
21 views

Moment of inertia question 11 [on hold]

A circular disc of radius $R$ and mass $M$ has non uniform surface mass density $ar^2$ where $r$ is the distance from the center of the disc and $a$ is a constant.what is the moment of inertia about ...
0
votes
1answer
30 views

Relativistic addition of velocities in the y-direction? [on hold]

I've been having some difficulty with the problem described below, please have a look: Two particles with identical masses (m) undergo a collision. Before the collision they move with velocities ...
0
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1answer
64 views

How to calculate the energy required to rotate a planet?

How to calculate the energy required to rotate a planet from non-rotating state? Say the planet is Venus with equally distributed mass of $4.8676 \times 10^{24}$ kg, and desired rate of 1 rotation per ...
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0answers
28 views

Identity for the product of propagators

Working in 1 spacial dimension, it has been written that $$\begin{align} \int K(x_f,x,t_2)K(x,x_0,t_1)dx &= \int \langle x_f|e^{-\frac{i}{\hbar}\hat{H}t_2}|x\rangle \langle ...
0
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0answers
33 views

How to write the energy for a system of beams? [on hold]

Goodmorning to everybody. In my problem I would like to write the energy of a system of 3 beams (see the link below), clamped together in A, positioned at 120° one to each other. ...
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0answers
14 views

What is the minimum required length of mirror to view full object if the mirror is convex?

i want to find the Radius of curvature of a convex mirror. i have all the factors to calculate except for image height of an object and image distane. so i can find the image height of an object from ...
2
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0answers
37 views

Feynman Propagator in Position Space through Schwinger Parameter

So I am aware of a thread at Propagator of a scalar in position space but it does not answer my question, which is more about poles in position space. Starting from $$D_F(x_1-x_2) = \int \frac{d^4 ...
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0answers
21 views

Inquisitive please help me!! Finding charge on plastic spheres [on hold]

A piece of wool is used to charge two plastic spheres. When the spheres are held 300mm apart, they repel each other with 9.00N of force. If the wool ends up with a surplus positive charge of 29.5μC , ...
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0answers
20 views

Dipole moment of a specific charge distribution

A negative charge cloud distribute as a ellipsoid and a positive point charge situated at the centre of the ellipsoid.What should be the dipole moment of charge distribution.I mean, if the negative ...
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1answer
32 views

Solving for the density operator in the quantum Brownian motion master equation

I want to solve for the density operator in the quantum Brownian motion master equation, \begin{align} \begin{aligned} ...
0
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2answers
58 views

Orbital Velocity Question

I have a satellite in a stable trajectory around Earth, of a Mass $m$. I know that its velocity is: $$ v = \sqrt{mG/r}\, $$ But now it begins accelerating directly against the gravity vector (i.e. ...
0
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2answers
38 views

Convert cubic feet per sec to feet per sec

Is there a way to convert cubic feet per sec to feet per sec. Or in general volumetric flow to velocity? I want to know the time taken by water to travel from point A to point B. I have the distance ...