Applies to questions of primarily educational value - not only questions that arise from actual homework assignments, but any question where it is preferable to guide the asker to the answer rather than giving it away outright. Please READ THE GUIDANCE IN META before asking homework questions.

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1answer
18 views

finding angle of intersection in terms of the angle between mirrors [on hold]

Two mirrors are joined end to end and tilted at an angle $\theta$ with respect to each other , you point a laser beam toward the first mirror which reflects it towards the second mirror , the beam is ...
1
vote
2answers
45 views

Which dumplings will be more salty?

There are two identical pots filled with different amounts of water (one has more water, the other one has less). The same amount of salt has been poured to each pot. The same amount of dumplings has ...
0
votes
1answer
21 views

Calculating $g$-force in between planets

The g-force is given by $1 + \frac{a}{g}$. The question is that a rocket is accelerating from between Mars AND Juptier at 26.95m/s. The astronaut in focus is 60kg (irrelevant I believe). Using this, ...
0
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0answers
18 views

A problem of thermodynamics [on hold]

A rigid tank contains a hot fluid that is cooled while being stirred by a paddle wheel. Initially the internal energy of the fluid is 800KJ, during the cooling process, the fluid loses 500KJ of heat, ...
-1
votes
1answer
20 views

Difference in the amount of heat produced in two circuits having two different metals

There are two circuits to the first nichrome is connected like this and in the other a copper wire instead of the nichrome wire when electricity is passed through which wire gets more heated? Since ...
0
votes
1answer
14 views

Voltmeter readings at different points in a circuit

I have a circuit with a 6 volt battery and 2 resistors A and B in that order.A has a potential drop of 2 volts and B has a P.D of 4 v. which means every electron moving across the resp. resistors ...
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votes
0answers
14 views

Current intensity [on hold]

i want an answer for First question : a and b And Second One , Saying Why you said that answer
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votes
0answers
28 views

Work done when lifting a bucket that is losing water [on hold]

A bucket of mass $m$ is filled with water of mass $M$ from a well of depth $h$. But there is a hole in the bucket from which water escapes at a uniform rate. When the bucket is pulled to the top of ...
1
vote
1answer
25 views

By what factor a planet travels (in circular orbit) faster than another

Question: It is known that radius of Neptune in a circular orbit around the sun is 30 times greater than that of Earth's. Does Neptune travel faster than earth and by what factor? Attempt: For a ...
1
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0answers
37 views

Determining Constant of Motion

On the phase space $\mathbb{R}^4$ consider the Hamiltonian $$H(x_1, x_2, p_1, p_2) = a(p_1^2 + x_1^2) + b(p_2^2 + x_2^2) + c(p_1 p_2 - x_1 x_2)$$ Find a constant of motion by showing that $H$ ...
0
votes
1answer
32 views

Why does the expression for this object's velocity have -T in it? [on hold]

The original question: At $t = 0$, an object of mass $m$ is at rest and at $x = 0$ on a horizontal, frictionless surface. A force in the $x$ direction: $$ F(t) = F(0) e ^{-t/T} $$ is ...
3
votes
0answers
27 views

Axion Model Field Theory Problem

This is a homework problem for a field theory class dealing with an axion model. Originally, we are given that $$S[a]=\int_Md^4x \frac{1}{2}(\partial_{\mu}a(x))^2$$ has a continuous global ...
0
votes
0answers
16 views

How would you construct a linear graph to determine the density of some material? [on hold]

The density $\rho$ of a solid is found by dividing the object's mass by its volume. If the masses and diameters of several coins are given and you are told that each coin has the same thickness and is ...
1
vote
1answer
26 views

How can I find an error formula for density? [on hold]

$${p} = \frac{4m}{πtd^2}$$ How can I find the error in this formula? I don't know where to begin. I know that I'm looking for the "partial derivative" of density to solve this, but that is a brand ...
-1
votes
0answers
16 views

Comparison of the classical and quantum distribution functions [on hold]

The distribution functions $f_{MB}(E)$, $f_{BE}(E)$ and $f_{FD}(E)$ all have the undetermined constant $A$ (= $\exp(-α)$ ). This may be viewed as a normalization constant, whose value can be found ...
-2
votes
0answers
27 views

Maxwell-Boltzmann speed distribution [on hold]

A container has $10^4$ $N_2$ molecules per $\text{cm}^3$. Assuming that the particles are distinguishable and $$A = \frac NV \left( \frac{m}{2 \pi k \, T} \right)^{3/2}$$ , Tabulate the values of ...
0
votes
0answers
14 views

how do I resolve this velocity into components? [on hold]

my problem is: And this is the diagram I drew to resolve it into its constituent R and theta forces: So I get \begin{align} V_r &= - V \cos \theta \\ V_\theta &= V \sin \theta ...
1
vote
0answers
18 views

Michelson-Morley Experiment, Time Dilation, Length Contraction assignment need help [on hold]

I have Physics assignment about Michelson-Morley Experiment, Time Dilation, Length Contraction need help. The question are in the pictures Thanks
0
votes
1answer
28 views

Calculating change in gravitational potential energy [on hold]

A satellite mass 500kg is elevated from altitude 10000km to altitude 20000km. Radius of earth is 6378km. Mass of earth is 5.97 * 10^24kg. Gravity is given to be 9.81m/s My attempt is using final mgh ...
2
votes
2answers
25 views

Loads in decelerating a falling object

I'm new here and haven't looked at physics in any real depth since high school, 8 years. so apologies for any obvious mistakes. I remove trees in confined spaces setting up rigging systems, I am ...
3
votes
1answer
43 views

Equation of motion for system of springs

I need to find the equations of motion for the following system. If $x_1$ is $m_1$'s extension and $x_2$ is $m_2$'s, then, I feel like for $m_1$ we just need to consider $x_1$ giving $$m_1 a_1 = ...
1
vote
0answers
17 views

flow through an orifice [on hold]

The surface area of a first orifice with 2 mm diameter is 3 mm$^2$. The surface area of a second orifice is 5 times bigger from the surface area of the first orifice (15 mm$^2$). How much would be ...
1
vote
0answers
54 views

Two boxes connected by a rope

Two boxes, $A$ and $B$, are connected to each end of a light vertical rope. A constant force of $70.0N$ is applied to box $A$. Starting from rest, box $B$ descends $11.6m$ in $4.40s$ The tension ...
1
vote
1answer
32 views

Finding the acceleration given only an angle

This is one of my homework problems for a College Physics I course: Dana has a sports medal suspended by a long ribbon from her rearview mirror. As she accelerates onto the highway, she notices ...
0
votes
2answers
45 views

Projections in Polar coordinate system

I really understand what projections in Cartesian coordinate system, I can imagine this, but I absolutely do not understand projection in polar system. For example, I have a speed, $U$, and I must ...
0
votes
1answer
43 views

The forces acting on 2 boxes [on hold]

Consider the following figure: The surface is not friction-less. When the force $F$ is applied on mass A: Is the force the mass A applies on mass B larger, smaller or equal then the Force that B ...
3
votes
0answers
28 views

Reduce density matrix for given eigenfunction [on hold]

My question is about how to find reduce density matrix for partition of given eigenfunction. Full question is just in image.
0
votes
0answers
23 views

Calculate depth of cone in water as water is poured inside the cone [on hold]

Consider a cone with radius $r$ and length/height $h$. A water container has volume $V$, and if needed dimension $d(x,y,z)$. This cone is put on the water, and water is slowly poured inside the ...
1
vote
2answers
38 views

Derivation of the average Velocity formula with constant acceleration (using calculus)

I have been looking at $$ v_{avg} = \frac{v_{i} + v_{f}}{2}, $$ when the acceleration is constant, where $v_i$ is equal to the initial velocity and $v_f$ is equal to the final velocity. How can ...
0
votes
0answers
23 views

How to calculate the ship resistance caused by water viscosity

If there is a ship going in the sea at 50km/h, and a length of 5m, width of 2m, how do I calculate the ship resistance caused by water viscosity? in other words I want to calculate the drag Force that ...
3
votes
4answers
282 views

If a truck collides with a car, can the truck experience a larger force?

I am confused, here is a question: A large truck and a mini bus both have same velocity V and they collide and stop. The collision lasts for 1 second. A) Which one of the two will experience ...
0
votes
3answers
68 views

If a body is floating in a static fluid, then the volume of the displaced fluid equal to the volume of the inmerse part of the object (proof)

Suppose an arbitrary body is floating in a static fluid, either totally or partially immersed in it, then the volume of the displaced fluid equal to the volume of the immersed fraction of the object. ...
0
votes
1answer
49 views

Why is the slippage constraint for one moving cylinder and one fixed cylinder $r(\phi - \theta)=R \theta$? [on hold]

Why is the slippage constraint for one moving cylinder and one fixed cylinder $r(\phi - \theta)=R \theta$? Every time I write it down on paper I get the result $r\phi = R \theta$. I am not sure if I ...
0
votes
2answers
28 views

Finding power in series circuit

A resistor of resistance 12 ohms is connected in series with a cell of negligible internal resistance. The power dissipated in the resistor is P. The resistor is replaced with a resistor of resistance ...
0
votes
3answers
103 views

How fast would the Earth need to spin for us to feel weightless?

It's a classic question with many answers all over the Internet, but none here so I figured I'd ask it: How fast would the Earth need to spin for a person (or anything for that matter) to feel ...
0
votes
1answer
44 views

Expectation value of number operator $\hat{n}$

I'm studying for my quantum mechanics test and I've stumbled on this problem. They want the expectation value of $\hat{n}$, $\langle \hat{n} \rangle$, with this given $\psi$ at $t=0$: $$ \lvert ...
2
votes
2answers
149 views

Energy to reach the moon

I've been stuck on this question for a couple of days now. Given that the potential energy of a 930 kg object on the Earth's surface is -58.7GJ, calculate the minimum energy required for the 930 ...
0
votes
0answers
37 views

minimum rope stiffness to keep person from touching ground(hooke's law) [on hold]

I thought a lot about this problem (However it's must be very easy ) At first, i would write the statement of problem and then my wrong solution. statement: Find the minimum stiffness of rope,so ...
-1
votes
0answers
33 views

Please tell me the way to solve the following question [on hold]

Question - Consider a box that is divided into two indentical parts of equal volume. The right half contains a gas of $N$ (=100, 500, 1000) particles and the left half is empty. A small hole is ...
0
votes
1answer
20 views

How do I find the moment of inertia of a regular $n$-gon? [on hold]

Of a regular $n$-gon with radius $R$ and mass $M$. Any hint to solving would also be acceptable. The result I'm looking for is $$I_{CM} = (1/2) MR^2 (1 - (2/3) \sin^2(\pi/n)).$$
0
votes
0answers
7 views

How to figure out new vector direction after deflection by polar and azimuthal angles [migrated]

I have a direction cosine vector in Cartesian 3D space. The vector starting point is (x0,y0,z0) and direction {i0,j0,k0}. I need to find the new direction cosine vector direction in the Cartesian 3D ...
0
votes
1answer
32 views

What are overtones and how do they relate to harmonics?

Problem 43. Two organ pipes, a pipe of fundamental frequency 440 Hz, closed at one end, and a pipe of fundamental frequency 660 Hz, open at both ends, produce overtones. Which choice below ...
1
vote
0answers
35 views

Find the field of two infinite strips of width $b$ [on hold]

Q:The two charged strips in the following picture have width $b$, infinite height,and negligible thickness(in the direction perpendicular to the page).Their densities per unit area are $\sigma$ ...
0
votes
0answers
14 views

What will be the electric field intensity? [on hold]

Ì have a problem here I tried to solve it but I am not able, so it goes like this. If the surface area is 10 cm2 and the electric flux is 25 NM2 C-1, find the electric field intensity?
1
vote
1answer
27 views

$c/a$ ratio for an ideal hexagonal close-packed (HCP) structure [on hold]

Show that the $c/a$ ratio for an ideal hexagonal close-packed (HCP) structure is $\left(\frac{8}{3}\right)^\frac{1}{2} = 1.633$. I believe $a$ is the length of $a_1$ and $a_2$. I figured that ...
1
vote
2answers
39 views

Solving equation of motion with exponential friction term

My friend's kid asked me this question. I have no idea how to solve it since I have stopped calculating mechanics for about 15 years since I graduated from high school. The question is: A boat that ...
1
vote
1answer
218 views

Advanced kinematics problem regarding $F = ma$ [on hold]

I really need help with this problem. Thank you for your time. Question: Look at the figure below. Derive the formula for the magnitude of the force F⃗ exerted on the large block (mC) in the ...
1
vote
1answer
32 views

A ball is dropped from the roof of a building. How fast is it moving after 4.9 seconds? (Absolute value) [on hold]

i really need help. A ball is dropped from the roof of a building. How fast is it moving after 4.9 seconds? (Absolute value) in m/s A water balloon is thrown downward from a tall building with an ...
-4
votes
0answers
30 views

Can human body survive a negative acceleration of $ 250m/s^2$ [on hold]

Can the human body can survive a negative acceleration trauma accident because of a sudden stop if the magnitude of the acceleration is less than $250m/s^2$. If you are involved in an automobile ...
0
votes
1answer
15 views

Flux through planes of a wind turbine [on hold]

The question asks how much wind will flow through each plane of a cube surrounding the turbine. the velocity of the wind is given by a function that depends on position according to v=(az,bz^2,c). The ...