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0
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1answer
23 views

Weight held by jet stream of water

Consider a bucket of weight $W$, held in air by a jet stream of water from the ground (moving vertically upwards) at height $h$. The water is fired from the ground at the rate of $\mu$ (units ...
0
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0answers
19 views

Tension on two string with one known angle and one known tension [on hold]

Consider a 50-N weight suspended by two wires as shown in the accompanying figure. If the magnitude of vector F1 is 35 N, find angle alpha and the magnitude of vector F2
0
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1answer
18 views

Gravitational Potential Energy to Kinetic Energy

When a yo-yo is released from a height $h$, the gravitational potential energy is converted to kinetic energy. However, the yo-yo obviously has less acceleration than $g$, $9.8\frac{m}{s}$. This means ...
2
votes
1answer
144 views

Is work is equal to $mv^2$ (without $\frac{1}{2}$)?

I was trying to come up with an equation for work that doesn't include time, because I don't know time. Here's what I did: $$ work = Fd = mad = m{v\over t}d = m{v\over\left({d\over v}\right)}d = ...
1
vote
0answers
38 views

Show that the profile of the hill is a cycloid [on hold]

I'm struggling with this problem: From George Simmons_ Differential Equations I've tried different things and I showed that the $x$ component and the $y$ component of the shadow should move with ...
3
votes
0answers
27 views

Equivalent Dose absorption from Na22 source

No idea what exactly the rules are or how I should ask this question, but here's the verbatim quesiton: "A Na$^{22}$ source has an activity of 100 $ \mu $C. If you handle the source, how big is the ...
0
votes
1answer
27 views

Calculating deceleration from a non-constant force [on hold]

As a background : I am trying to design a spring to locate at the end of a zip-line (flying fox) to decelerate a person slowly. I am having some trouble working out the deceleration because it ...
0
votes
0answers
17 views

Solving for currents in a circuit [on hold]

I need help finding the three listed currents in the figure below. Attached on the bottom is the solution for this problem, however I do not quite understand how they came up with the answers. ...
0
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0answers
55 views

How many atoms make up the average ant? [on hold]

Given an ant is anywhere from three to five milligrams,
0
votes
1answer
69 views

What distance does one travels in his lifetime? [on hold]

I think this isn't answerable without having point of reference from which speed at which earth travels in space, however if I am wrong the please give absolute distance. Considering that earth spins ...
0
votes
1answer
21 views

A Conversion problem featuring Significant figures [on hold]

What is the speed of a car going v=1.000 mile per hour in SI units? You can do each conversion separately. Use the facts that 1mile=1609 meters and 1hour=3600 seconds. Express your answer in meters ...
1
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0answers
20 views

Unsure how resistors are connected? (Series/Parallel) [duplicate]

I am currently attempting this practice question in my tutorial and while I am able to reduce the circuit below to I do not know whether the 6/6/6/6 pane is connected in series or parallel, it ...
-1
votes
1answer
32 views

equivalent spring constant for a nonlinear spring force [on hold]

The force-deflection relation of a steel helical spring used in an engine is found experimentally as $F(x) = 200x + 50x^2 + 10x^3$, where the force $(F)$ and deflection $(x)$ are measured in pounds ...
1
vote
1answer
38 views

Resistors in para and series circuit, finding volt [on hold]

How anyone know how to do the question? I know how to reduce it to a window pane of 6/6/6/6 with a 3 in series but i have no idea how to do it. Well i did manage to reduce the right side of the ...
0
votes
3answers
39 views

Distance covered - variable acceleration [on hold]

Question: A point moves in a straight line under the retardation $av^2$, where $a$ is a positive constant and $v$ is speed. If the initial speed is $u$, the distance covered in $t$ seconds is: a) ...
4
votes
3answers
103 views

Different results to a basic question ( Newton's law and perservation of momentum)

Trolley with mass of $m_0=1 \ kg$ is moving without friction on the railway track. It is raining so there is a constant mass flow of water $\Phi_m=0.1\ kg/s$. Constant force $F=0.1 \ N$ is ...
-4
votes
0answers
21 views

Capacitance of air capacitor [on hold]

Hi I'm currently working on the following question (image below), any help is much appreciated!
0
votes
1answer
44 views

A moving inclined plane with block problem

I'm trying to solve for a challenging problem : a moving inclined plane with a block I want to solve for the acceleration components for the block and the plane and the normal force acting on the ...
0
votes
2answers
40 views

equivalent spring constant for a drum floating in water

If I have a drum floating in water, how do I find the equivalent spring constant? I know that the water has density $\rho$, the drum has diameter $d$ and height $\ell$, and the positive direction is ...
0
votes
1answer
31 views

Deviation from 2D trajectory

I need to find out how far a ball is from the predicted trajectory in 2 dimensional space and I know the start and end position of the ball in both dimensions. Along with that I know the initial ...
-3
votes
0answers
27 views

Solve the following linear second order circuit [on hold]

I am not able to solve for the second part of the question (when v(t) = 0)
0
votes
0answers
19 views

Calculate object displacement with a radial/centripetal acceleration [on hold]

What i want to do is calculate the displacement of a object with a certain radial acceleration in a moment of time. The object has a velocity, radial acceleration and a tangential acceleration. For ...
-2
votes
1answer
30 views

What formula connects the moment of inertia and angular velocity? [duplicate]

I need to determine angular velocity of a disc when a man with given mass and speed whacks on the edge of it. I calculated the total moment of inertia of disc and body, how do I calculate the ...
5
votes
2answers
325 views

The acceleration vector of a simple pendulum

In this picture the acceleration vector $\vec{a}$ points upward when the pendulum is halfway Click To see animated GIF But according to this picture, the force acts tangentially: Which means the ...
3
votes
1answer
108 views

Forces acting on two balls in a jar [on hold]

Consider the following situation: Two balls are inside a jar with diameter $D$. The balls are uniform in mass and both have the same diameter $d$. Express the forces that acts at the colored dots ...
1
vote
2answers
32 views

Followup to: The relation between energy quanta of an Einstein solid and the equipartition value of heat capacity

As a followup question to this question: The relation between energy quanta of an Einstein solid and the equipartition value of heat capacity and this answer ...
0
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0answers
30 views

How do charges actually distribute among capacitors? [on hold]

Two capacitors of capacitance $3 \mu F$ and $6\mu F$, are charged to potentials of 2 V and 5 V respectively. These two charged capacitors are connected in series. Find the potential across each of the ...
0
votes
1answer
20 views

Torque due to a magnetic field

We have two infinite perpendicular wires, each carrying a current "i" and the distance between them is l. If both the wires are free to move, how will they arrange themselves because of the torque ...
0
votes
0answers
57 views

Differential Equations [on hold]

$$ \nabla^2 B = - \mu_0^2 \epsilon_0^2 \frac{\partial B}{\partial t} $$ $$ \nabla^2 E = \mu_0 \epsilon_0 \frac{\partial B}{\partial t} $$ Find as many E and B field solutions as you can from this. ...
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votes
2answers
60 views

Unit conversion from km to mm [on hold]

I'm a bit rusty on my unit conversion skills and I need help figuring out what I did incorrectly converting 9.06 x 10^8 km into mm. Here's what I did: 9.06 x 10^8 km x (1 meter/10^3 km) x (10^-3 km/1 ...
2
votes
1answer
35 views

The relation between energy quanta of an Einstein solid and the equipartition value of heat capacity

Consider an Einstein solid with quantized energy values $U=q\epsilon$ and $N$ oscillators. I calculated some values of an Einstein solid numerically through a function in R (at the bottom of the ...
1
vote
1answer
60 views

An oscillating skateboard

A half pipe of a skateboard park consists of a concrete trough with a semicircular section of radius 5m, I hold a frictionless skateboard on the side of the trough, pointing down toward the bottom and ...
0
votes
0answers
44 views

Infinite Atwood (pulley) system - what's wrong with this? [on hold]

Each block has mass $m$. We are finding acceleration of topmost block. Assume the tension $T$ acting on topmost block and acceleration $a$ in upward direction. Then tension on second block is ...
0
votes
2answers
33 views

Bulk Modulus, How are these formulas equivalent?

Bulk Modulus is defined as $$ B = \frac{VdP}{-dV}$$ Where $V$ is volume and $P$ is pressure. It is also defined as, $$ B = \frac{\rho dP}{d\rho}$$ Where $\rho$ is density. Question: How are these ...
-1
votes
0answers
49 views

Ball thrown vertically upwards in a moving train [on hold]

A person sitting in the compartment of a train moving with uniform speed throws a ball upwards. What path of the ball will appear to him ? What to a person standing outside?
-2
votes
0answers
42 views

Electricity Problem [on hold]

A power Station Is Connected To A Factory 2.5 km Away By Two Wires the potential difference between the terminals of the wires at the station is 240v and that for the other terminals at the factory ...
0
votes
3answers
40 views

Perceiving travel speeds from different view points

Scenario: Two vehicles pass each other on a highway moving at 100km's an hour; from a stationary position beside the road you witness these cars pass each-other directly in front of you: from your ...
0
votes
0answers
28 views

electrical potential [on hold]

The electrical potential at a distance r from a point charge, Q, is given by the function $$V(r)= \frac{Q}{4 \pi \epsilon_0 r}$$ (i) What is the gradient of this function? (ii) What is the ...
3
votes
5answers
319 views

Commutator algebra in exponents

Considering $X$ and $Y$ such that $[X,Y]=\lambda$, which is complex, and $\mu$ is another complex number, prove: $$e^{\mu(X+Y)}=e^{\mu X} e^{\mu Y} e^{-\mu^2\lambda/2}$$ My attempt (so far) is: ...
0
votes
0answers
31 views

Entropy of an oscillator in Einstein's solid

This is a homework problem and I need help with it. A solid's (Einstein's model) oscillators are in the first excited state on average. How much entropy does one oscillator have? What I've tried so ...
1
vote
0answers
107 views

Textbook disagreement on geodesic deviation on a 2-sphere

Apologies if I have this completely wrong (and for the general long-windedness). I've searched online but can't find anything helpful/relevant. I'm trying to use the geodesic equation ...
0
votes
1answer
51 views

Resistance and amperage [on hold]

My problem is to solve the following exercise. First, if $R1 = R2$, then $I1 = 1.0\,\text{A}$. Now I have to find $I1$ if $R2 = 2 R1$. If $R1 = R2$ then I have got for the total resistance ...
0
votes
1answer
45 views

Penetration of a bullet into a wall

In which of the following situation will the bullet of the pistol penetrate deeper in the wall? Why? Alternatively will the penetration in both cases be the same? Can you explain the concepts behind ...
-1
votes
0answers
24 views

A ball rolling in a bowl [on hold]

There is a small ball with a radius of 2 mm inside of a bowl with a radius of 22 mm. If the bowl is tilted 1 degree in any direction, what does the slope of the bowl need to be in order to get the ...
2
votes
1answer
56 views

A beam of light, traveling around a planet

Some time ago, I happened to have found one problem: The refractive index of the planet's atmosphere decreases with height above the surface under the following law: $$n=n_0-\alpha h$$ ...
1
vote
0answers
34 views

Length of the missing part [on hold]

I have got a very interesting question. A car is driving this way on the picture down. In the looping is a missing part. The radius of the looping is r = 40cm. The car starts at the height h = 3r. If ...
0
votes
0answers
21 views

How to find a vector normal to a cylinder in cylindric coordinates? [migrated]

I'm trying to solve a problem which demands to multiply a vector M and vector normal to a cylinder's surface in cylindric coordinates. Height of the cylinder is infinite and its radius is R. So how do ...
1
vote
1answer
95 views

Magnification of an astronomical telescope not in normal adjustment?

I am stuck on this question: A telescope consists of two thin converging lenses of focal lengths 100cm and 10cm respectively. It is used to view an object 2000cm from the objective. What is the ...
1
vote
0answers
10 views

What are the thermal properties of a “perfectly rigid” container?

can a "perfectly rigid" container be a diathermal boundary? I checked the wikipedia article for heat and read: Kinetic theory explains transfers of energy as heat as macroscopic manifestations of ...
0
votes
0answers
27 views

A Nutcracker problem [closed]

Consider a nutcracker, with a ball-shaped nut like shown in the figure: I want to find the minimal coefficient of friction, $\mu _{min}$ so that the nut would not slip between the two levers. So, we ...