Relative Definition and 1000 Threads

I have been told that relative velocity can be negative on this forum, so i would like to ask a few questions based on this. scenario 1) Two observers O and O' are facing each other and are approaching each other. O sees O' approaching at v=0.5c and vice versa. The vector of the velocity is...

According to special relativity, KE= ([PLAIN]https://upload.wikimedia.org/math/3/3/4/334de1ea38b615839e4ee6b65ee1b103.png-1)(mv^2)/2. Since the velocity measured is dependent on a person's frame of reference, then does that mean energy too is dependent on frame of reference? For example, if an...

Hi, I'm reading about 50% relative humidity in my house about 10 kilometers (6.2 miles) away from the sea. How can water vapor from the sea reach me 10 kilometers away? I'm expecting zero or very low relative humidity.. does it mean if you live the ocean, you won't get relative humidity below...

Let's say you have a planet rigged to explode only if two bowling balls hit respective sensors at the same time. An unfortunate observer, call him Carl, releases two bowling balls at the same time from his reference frame. Meanwhile, Shirley passes by at nearly the speed of light. From Shirley's...

For the uncertainty about relative atomic mass. Such as for H-1 there is 1.00794(7)u. what exactly does the "7"means? Is it 1.007947? or 1.00794(+/-)0.000007? or something else? ref: http://www.ciaaw.org/pubs/TSAW-2007.pdf

Homework Statement Imagine that space (not spacetime) is actually a finite box, or in more sophisticated terms, a three-torus, of size ##L##. By this we mean that there is a coordinate system ##x^{\mu}=(t,x,y,z)## such that every point with coordinates ##(t,x,y,z)## is identified with every...

Homework Statement For problems 1 and 2 use http://T: R^3 to R^3, T(<x1,x2,x3>) = <2x1-x2, x2+3x3, x1 - x2+2x3>, , T: R^3 to R^3, T(<x1,x2,x3>) = <2x1-x2, x2+3x3, x1 - x2+2x3>, , bases B = { <1,0,1>, <1,1,0>, <0,1,1> } and B' = { <1,1,-2>, <2,1,-1>, <3,1,1> }. Find T ( <3,-1,2> ) by using...

I saw this problem in my dynamics class: http://d2vlcm61l7u1fs.cloudfront.net/media%2Fa22%2Fa2261e7a-0e85-45e7-8b63-f23157d623bc%2Fphp37ql1a.png I know how to solve it, but I don't understand why A(bd) has both a normal and tangential component to acceleration. If it is rotating at a constant...

Homework Statement What is the angle of twist at gear A relative to the motor? (Round to the closest 6th decimal) Homework Equations I know to find the angle its θ = ∑ (TL/JG) but it can also be θ = Lτ/Gr The Attempt at a Solution So i used both these equations, and I got...

Homework Statement Homework Equations vx = 70*cos(α) + 8.333 (30 km/h = 8.333 m/s) vy = 70*sin(α) vx*t = 350 vy*t = 60 -(1/2)*g*t^2 + vy*t + 2.5 = 60 The Attempt at a Solution This problem is conceptually very simple for me, but I can't solve it without using a solver like Wolfram Alpha...

Homework Statement [/B] If bar AB has an angular velocity of 6 rad/s, determine the velocity of the slider block C at the instant shown. 2. Homework Equations The Attempt at a Solution vB=vA+wABxrB/A vA=0 vB= -0.8485i+0.8485j So then C relative to B: vC=vB+wBCxrC/B -vCi=...

Dear PF Forum, I have a confusion about gravity. And frankly I don't know if this question belongs to this sub forum (cosmology, general physic?). Gravity attracts object - Newton Gravity curves space time - Einstein. Why we revolve around a massive object? Because that massive object curves...

Homework Statement A 52kg man is on a ladder hanging from a balloon that has a total mass of 450kg (including the basket passenger). The balloon is initially stationary relative to the ground. If the man on the ladder begins to climb at 1.2m/s relative to the ladder, (a) in what direction does...

Find local maxima and minima for 6${x}^{3}$+6${x}^{2}$-8x. I found that (-1.08,8.08) is max, (0.41,-1.86) is min. Where i was wrong?

Hi, Could i please get advice on this problem and confirm that my approach and solution are correct? Thanks in advance. 1. Homework Statement An enemy space rocket traveling at speed 0.8c towards the planet Zog fires a missile in the direction parallel to its own path. Relative to the rocket...

Homework Statement The distance between cities A and B it's L. An airplane flies back and forth between A and B, in a straight line, with velocity V in relation to the wind. So, calculate the total time of the flight, if the wind blows with velocity v, in a direction which forms an angle theta...

Mentor note: moved to homework forum later, therefore no template.[/size] When doing a rigid body relative motion (accel) problem using vector analysis, how do I know when it's appropriate to substitute sin/cos values vs when to use just the numbers given as the velocity?

There's something I don't manage to understand in the union between the relativity of simultaneity and the uncertainty of a quantum system's state. Observer A is in a lab on Earth. Observer B is approaching Earth at half the speed of light. On Earth, we build an experiment that gives a result...

Homework Statement Amy is traveling at 60mph on the highway, due North. The on-ramp nearby starts out going West, and then curves around so that eventually it is also North, parallel to the highway. A) Bob appears, traveling 40mph going West (on the onramp). What is his speed relative to Amy...

Homework Statement A ball rolls with a velocity of 14 mm/s [W] on a board that is being pulled [E 60o N] at 20.0 mm/s. What is the velocity of the ball relative to the floor? b = ball x = board f = floor Homework Equations V_bf = V_bx + V_xf The Attempt at a Solution I tried to work through...

I have a question about relative voltages and operating points of components, in this case tubes. Are these two functionally the same? For a while now I never could understand how the bottom triode of the WCF in an amp I bought was biased at -100v on the grid and 0 volt on the plate which...

Can anyone answer this question: In the context of GR, If two objects are in collinear free fall, far enough apart so that the field intensity differs for each object, and one measures the relative velocity between the objects in the coordinate system of the objects using (say) a radar system...

Homework Statement A boat propelled so as to travel with a speed of .5m/s in still water moves directly across a river that is 60m wide. The river flows with a speed of .3 m/s. At what angle relative to the straight across direction must the boat be pointed? How long does it take the boat to...

Homework Statement An 18.5kg box is slid up a 5.6m long ramp that makes an angle of 33 degrees with the floor. What is the gravitational potential energy of the box relative to the floor? Homework Equations Ek = 1/2mv2 The Attempt at a Solution My teacher gave me an answer of 550J, but I'm...

... in order that one's clocks will lose: (a) 1 second per day as observed from S? (b) 1 minute per day as observed from S? I was referencing this:( http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/tdil.html#c2 ) hyperphysics page but I still can't seem to understand what I need to do to...

Homework Statement You are traveling on an airplane. The velocity of the plane with respect to the air is 160 m/s due east. The velocity of the air with respect to the ground is 41 m/s at an angle of 30° west of due north. 1) What is the speed of the plane with respect to the ground? Homework...

The question asks "The kinematic equation d=vt is used in conjunction with relative velocity questions. Explain why the other kinematic equations are not useful for most relative velocity questions." I assume the answer to this is that most relative velocity questions that I deal with assume...

Homework Statement A boy and a girl both swim at 3.0m/s. They jump into a river 1.0km wide, with a current of 2.0m/s[E]. a.) The girl swims so that she ends up directly across from her starting point. What is her velocity relative to the ground? Homework Equations Note: V = velocity with...

Hello Forum, We are on planet Earth that is rotating at an angular speed of omega = 7.27 × 10-5 rad/s. The Earth atmosphere is also rotating with Earth at the same speed (that is why it is at rest relative to the Earth surface). Let's say I have a coin in my hand that is 1 meter above the...

Homework Statement A canoe has a velocity of 0.420 m/s southeast relative to the earth. The canoe is on a river that is flowing at 0.550 m/s east relative to the earth. This can't be seen in the problem statement, but the angle between the two vectors is 45 degrees. As implied by the question...

Homework Statement Air is drawn into a compressor at normal temperature and pressure (N.T.P.) and compressed to a pressure of 6 bar gauge. After compression the air is delivered at 1.2m3 min–1 and cooled to a temperature of 30°C, at which point condensate is collected at the rate of 2 litres...

Dear all, I am trying to understand the plot below: http://supernova.lbl.gov/PDFs/expansionhistoryphystoday.pdf by S.Perlmutter. However, I don't get the meaning of the "relative brightness" of SN. How is it calculated? Is the brightness of each SN compared to a special one?

Homework Statement If the area of a rectangular field has length of 110 m and 80 m.If a spaceship is traveling with 0.9c velocity along the diagonal of the field.Then what is the area of the field seen by the astronaut in the spaceship? Homework Equations L=L(initial) Root over (1- (v/c)^2)...

A receptacle has a mass of 3 kg when it is empty, 53 kg when it is filled with water, and 66 kg when it is filled with glycerin. Calculate the relative density of glycerine. I know the formula to find out the relative density. d= absolute density / reference density ( 1000kg/m3)

Hi Folks, I am struggling to see how eqn 4.1.17 is arrived at using using eqn 4.1.10 at bottom of attachment. Its not clear to me what \frac{d \phi}{dt} is...apart from what is given in eqn 2.1.30... Any ideas? Thanks

Homework Statement Plot the following function in maple (any graphics software): I_\theta = I_m (cos (\beta))^2 \left( \frac{sin(\alpha)}{\alpha} \right)^2 Homework Equations Range = -20 degrees to 20 degrees \beta = \frac{\pi d}{\lambda} \sin(\theta) \alpha = \frac{\pi a}{\lambda}...

Molar mass is the mass of one mole of atoms of the element . Relative mass is average mass of one atom of that element compared to 1/12 of mass of one carbon-12 atom I don't understand how they are equal. Can someone explain to me please?

Homework Statement An observer on the ground sees a person on a train just leaving the station in the east direction. explain how the observer on the ground could see the person moving to the west while the train is moving east Homework EquationsThe Attempt at a Solution At first I thought...

[Mentor's note: Split off from this thread] Distinguished members I am not a physicist, so I cannot make a comment. I can only put my doubts and views. In most of the explanations or examples of time dilation given on internet, the source of light and the ray of light emitted from it travel in...

I'm looking at my American Gut results. The last column shows the relative abundance of bacteria. #taxon relative_abundance...

I understand that if someone is traveling away from Earth at a very high speed, time will slow down for the traveler relative to the people on earth. However, why is it not the other way around? If there is no universal reference frame, could this situation not also be thought of as the traveler...

I am looking to correct my understanding about the relative abundance of particles and antiparticles created before the two periods of annihilation: (1) protons/neutrons and anti-protons/anti-neutrons, and (2) electrons and positrons. In a previous thread...

I want to calculate the distribution function for the relative velocity v_r = v_1 - v_2 of two particles. Each particle velocity follows the Maxwell distribution for velocities. They have the same mass and temperature. Can I just multiplicate the Maxwell distributions of the two particles (and...

I think the equation for the relationship of the E (electrical) and B (magnetic) fields in electromagnetic (EM) radiation is E=Bc, where c is the speed of light. I think this is correct, but what does it tell us? On it's face, it looks as though the B field (of a photon, say) is...

Homework Statement (a) Using elementary Newtonian mechanics find the period of a mass m1 in a circular orbit of radius r around a fixed mass m2 (solved, but placing for context). (b) Using the separation into CM and relative motions, find the corresponding period for the case that m2 is not...

I would like to know if an infitesimal unit of time is relative or absolute. If a supernova sweeps away the Pillars in the Eagle Nebula, would it be correct to imagine that as I type this the gas/dust is being displaced or otherwise altered at the exact same instant even though images obviously...

Homework Statement As shown in the picture, two pulleys are riveted together with a known velocity. I need to find the velocity of two other points. Homework Equations V_A = VB + <ω> x <BA> V = ωr The Attempt at a Solution I've honestly been trying to figure this one out for over a...

Homework Statement The focal length of the objective lens is 25 mm, that of the eyepiece lens is 73 mm , and the two lenses are 200 mm apart. The object is 30 mm away from the objective lens. What is the image distance relative to the eyepiece lens? What is the overall magnification of this...

I want to know that are there any materials or methods by which their relative magnetic permeability (μr) be instantaneously,continuously & periodically varied. Kindly provide the reference document/video for the description if possible.

Why do we multiply permittivity of vacuum with relative permittivity? What does this calculation mean?