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32 views

Can any one help? [on hold]

Just over looking some extra physics questions I came to one which looked easy but difficult to attempt: Just as traffic lights turns green a waiting car starts it's motion with constant ...
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0answers
27 views

A typical puzzle like problem in electrostatics [on hold]

Imagine a classic wall clock in which -1 coulumbs of charge are present at the place of the 1st hour indicator and -2 at the place of 2nd hour indicator and so on (as seen in the picture below, ignore ...
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1answer
27 views

Apparent weight on a hill and in a ditch [on hold]

first time posting. I'm trying to solve these 2 problems. I have a solutions I just don't know if I'm right...seems odd that they are the same answer... 1) If you are driving over a hill of ...
1
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0answers
33 views

How to calculate launch angle for tangentially launched satellites?

What is the value of theta for a satellite not falling back to the Earth if it is launched from the direction tangent to the surface of the Earth? I have found the escape velocity which is 11.18km/s, ...
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0answers
18 views

ODE envolving current [on hold]

I have to do this exercise: 9. The current $I(t)$ at time $t$ flowing in an electric circuit obeys the differential equation $$I''(t) + RI'(t) + I(t) = \sin \omega t$$ where $R$ and ...
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0answers
75 views

Derivation of (2.45) in Peskin and Schroeder

I'm having trouble understanding the step $$\left[\pi (\vec{x},t),\int d^{3}y ~(\frac{1}{2} \pi (\vec{y},t)^{2}+\frac{1}{2}\phi (\vec{y},t)(-\nabla^{2} +m^{2})\phi (\vec{y},t)) \right]$$ $$ =\int ...
3
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1answer
39 views

Rotating hoop with fixed body inside of same mass [on hold]

Please help me to solve this problem. I am unable to understand which force will cause the hoop to bounce. A small body $A$ is fixed to the inside of a thin rigid hoop of radius $R$ and mass ...
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1answer
27 views

I want to find velocity of an object in parabolic path but Given = Initial and final position of object and gravity in $x$ direction? [on hold]

Need to find velocity in parabolic path. Given= initial and final position of object only and nothing else. Gravity is also present. i am coding an app of basketball and i want to throw the ball ...
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4answers
95 views

Is it possible to prove that projectiles with drag will not travel in a parabola under the theory of classical mechanics?

Can you prove that projectiles will travel in a parabola, provided the acceleration due to gravity $g$ does not vary significantly along the trajectory? This should take air resistance into account. I ...
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2answers
57 views

How to calculate the charge on a capacitor [on hold]

I have a network in which $C_1$ ($8.73 \;\rm \mu F$) and $C_2$ ($2.46 \;\rm \mu F$) are connected in parallel and $C_3$ ($7.45 \;\rm \mu F$) and $C_4$ ($2.22 \;\rm \mu F$) are connected in parallel. ...
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0answers
17 views

electronic circuit [on hold]

Sketch the circuit of a communication system incorporates a circuit that passes a signal whose centre frequency is 1kHz. The circuit has a quality factor of 5 and an attenuation of 40dB/decade. Using ...
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0answers
16 views

Weight of 1 Liter Ethylene at 2000 bars pressure [on hold]

I was wondering the weight of 1 liter of ethylene at 2000 bars and 310 degrees Kelvin? I have tried to just multiply the weight at 1 bar with 2000 but I don't think i got the correct answer because ...
1
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1answer
24 views

How to calculate required energy to displace a pendulum?

How can one calculate the amount of energy needed to displace pendulum with given mass m and string length L to $\alpha$ degrees from resting position when acceleration due to gravity is known?
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1answer
40 views

Maxwell calculations that predicted the generation of waves (further use for wireless telegraphs)

At this point in this documentary about the history of electricity: https://www.youtube.com/watch?v=oPnS2WO2_0k&t=4m40s the guy says the Maxwell calculations predicted the generation of certain ...
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2answers
52 views

Fluid dynamics - Water level in a container

An open container is being filled with water from the top at a constant volumetric flow rate $300 \frac{cm^3}{s} $. At the same time, water is leaving the container trough a circular whole at the ...
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0answers
40 views

How can metals like magnesium and sodium burn underwater? [on hold]

I can't find the answer anywhere else and I need it for an essay (I'm in 8th grade). Please answer with as much detail as possible. Any websites I have found have conflicting answers. One said that ...
0
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1answer
25 views

Calculate the weight that a hot air balloon can carry [on hold]

Given a hot air balloon of radius 10 meters and negligible mass, calculate the maximum weight it can carry if the density of outside air is 1.2 $\frac{kg}{m^3}$ and the density of inside air is 0.9 ...
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0answers
44 views

Classical mechanics problem [on hold]

I have the following problem, it says: A homogeneous disc of mass $m$ and radius $a$ rotates around its fixed center $o$. Its initial angular velocity $\vec{\omega_0}$ forms an angle $\alpha$ with ...
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1answer
82 views

Inertia tensor of a spherical cap

I'm trying to calculate the inertia tensor of a spherical cap (a piece of a sphere) like the one shown below. The origin (not shown) is located at the center of the whole sphere and the axes ...
-2
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0answers
20 views

how describe the curve [duplicate]

this curve describe relationship between Re and nf. when Re increase nf decaying .we find improve in TE and TM about the previous
0
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1answer
52 views

Need one more clue to find out $\theta$ [on hold]

For a elastic collisions in a square board , Let we have given two ball, one is black and another is white. The mass of the two ball is given below. After the collision, the black one goes to the ...
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3answers
34 views

Kinetic energy relationships with momentum and mass [on hold]

If I have some arbitrary particle, we will call particle 1 and another particle 2 that have the same momentum, yet particle 1 has half the mass of particle 2, how does the kinetic energy compare ...
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0answers
24 views

What is the value of the putty mass [on hold]

A block with mass M attached to a horizontal spring with force constant k is moving with simple harmonic motion having amplitude A1. At the instant when the block passes through its equilibrium ...
1
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0answers
37 views

Supercritical Steam Expansion [on hold]

Ten kg of steam at 500 bar is expanded at constant pressure until its volume increases to seven times its initial value of 0.01 $m^3 $. (a) Calculate the initial and final temperature of the steam ...
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0answers
35 views

A question about deriving Eq. (6.2.13) in Polchinski's string theory book volume 1

I have a question about deriving Eq. (6.2.13) in Polchinski's string theory book volume I. It is claimed that Now consider the path integral with a product of tachyon vertex operators, ...
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0answers
36 views

How to describe curve? [on hold]

How to describe curve in this picture ?
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0answers
31 views

Hi guys can someone enlighten me for these qns? [on hold]

I'm sort of newbie in solving these physics qns can you guys give me a step by step guidance to these qns? I've attempted but somehow i don't get the answers my lecturer has given. Thanks in advance. ...
1
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1answer
58 views

i can't detect what wrong have i done in a kinematics problem [on hold]

a question was given to us in assignment which was as follows A person moves 20 metres towards north then 30 metres towards east and then moves 30 x 1.414 metres towards south west. The whole ...
0
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0answers
15 views

What is the critical angle for this interface? [on hold]

Consider a TE wave with amplitude E0 incident on an air-dielectric interface from the dielectric side. The dielectric has an index of refraction, n1, of 1.6. The angle of incidence is 5° larger than ...
0
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0answers
17 views

Doped semiconductor problem [on hold]

I have to solve the following problem: If I have germanium doped with gallium, the energy level of the acceptor impurity is 0.011eV above the top edge of the valence band. If at room ...
0
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0answers
8 views

Time for which a battery will last if load and battery capacity is know [on hold]

I have problem where I know the battery capacity and the average load that is connected to the battery. Variables Capacity: 2000mah Load: 100ma How long will the battery last with this load? ...
2
votes
1answer
33 views

Period of pendulum in falling lift

A simple pendulum suspended from the ceiling of a stationary lift has period $T_0$. When the lift descends at steady speed, the period is $T_1$. When the lift descends with constant downward ...
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1answer
15 views

Determine stationary angular velocity of wheel with circuit in magnetic field

I have a wheel (free to spin around the $z-$axis) with four spokes that is connected by sliding contacts to a circuit with $U_0 = 0,72V$. Also, there is a B-Field parallel to the $z-$axis For the ...
0
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1answer
60 views

$\theta '' = \frac{a}{R}$? [on hold]

Assume that this is a general circular motion where $\theta$ is a function of time. I've derived some equations below and found that the angular velocity in the end is zero. Which step of my ...
2
votes
0answers
118 views

Question about an integration by parts in Feynman's Quantum Mechanics [on hold]

I have begun reading Feynman & Hibbs Quantum Mechanics and Path Integrals. Knowing little about variational calculus or Lagrangians I found the following integration by parts opaque. I think if I ...
1
vote
1answer
66 views

Tensors in special relativity [duplicate]

I'm trying to understand tensors, but I've come across the following question: Let $T^{\mu\nu}$ by a $(2,0)$ tensor. Give the definitions of $T_\mu^{\,\nu}$, $T_{\mu\nu}$, and ...
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2answers
94 views

Kinematics question - Newton's Law of Motion

Question: Find the mass M of the hanging block in the following figure which will prevent the smaller block from slipping over the triangular block. All the surfaces are frictionless and the strings ...
0
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1answer
29 views

Kinematics - moving body [duplicate]

If I have an inclined plane, which has acceleration $\alpha$, will a block placed on the inclined plane slip back with the same acceleration? (considering that the surface is frictionless)
0
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3answers
73 views

Image formation (lenses)

I have a question regarding image formation by lenses. It is the following: A lense with a focal length of $-48.0cm$ forms an image $17.0cm$ to the right of the lense. Where is the object positioned? ...
0
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2answers
35 views

Can clouds quench thirst? [closed]

Suppose you are standing on a mountain surrounded by clouds. You open your mouth and try to swallow the clouds (it's crazy, but still). Can the droplets of water in the form of vapor actually be ...
0
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0answers
36 views

Finite Square Well Inside an Infinite Square Well

Ok here's a potential I invented and am trying to solve: $$ V(x) = \begin{cases} -V_0&0<x<b \\ 0&b<x<a \\ \infty&x>a \\ \end{cases}$$ and $V(-x) = V(x)$ (Even ...
1
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2answers
52 views

who will win a race between man, horse and car of same power

Other day I got into a chat with my friend on work power and energy where he asked an intelligence related question the question was like this if a race was conducted between a man a horse and a ...
2
votes
1answer
44 views

Power required to keep a freezer at constant temperature

Alright, I'm completely stuck on this and so is everyone else I've asked. A freezer has a temperature Tc = -23℃. The air in the kitchen has a temperature Th = 27℃. The freezer in not perfectly ...
0
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1answer
24 views

An optical system with image from a convex lens forming behind a concave lens

I am having a problem drawing optical ray lines for optical systems. Namely, one which have a formation of image of the first lens beyond the second lens. Take the picture below as an example: In ...
1
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0answers
32 views

Why a transistor is activated when I touch its base with my finger? [closed]

Is my body charged eletrically? If so, how much? Will it work with all types of transistors?
0
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1answer
70 views

How to discover the $F = m\cdot a$ equation from scratch? [duplicate]

Is there a paper or a book that conceptually 'discover' the Newton's famous formula? I've been thinking about this equation, and I really don't know it for sure. Did Newton empirically noticed that ...
1
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1answer
24 views

Work done in pulling a rope from a boat

A boy sitting on a boat pulls on a rope with a constant force $F$ over a duration of time $t$. The other end of the rope is either tied to a bridge or to another freely floating boat of equal mass. ...
1
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0answers
29 views

Dipole charge attractions while one of them is turning around other [closed]

There is a electric dipole which is fixed. So angular momentum isn't conserved. And there is charge $Q$ which has initial velocity $u$. My question is: What is the tangential velocity of the charge ...
-2
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0answers
40 views

Modern physics one of the important question [closed]

The specific charge of cathode ray remains always constant but not for the positron, why?
-1
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1answer
44 views

average speed, speed and time [closed]

Jerome normally travel on a freeway from city A to city B at an average speed 85km/hr and his trip took him 2 hours and 25 min. one day with heavy traffic, slows him down and drive the same distance ...