Change Definition and 1000 Threads

When you look at an object, say, for example, 30 feet away, your eyeballs adapt to focus at that distance of 30 feet. When you look at the same object through a pair of binoculars, at what distance do your eyeballs adapt to focus at? Is it more or less than 30 feet? This is not a question...

Hi everyone, sorry for the basic question. But I was just wondering how one does the explicit coordinate change from dxdy to dr in the polar-coordinates method for solving the gaussian. I can appreciate that using the polar element and integrating from 0 to inf covers the same area, but how do...

Homework Statement The graph shows the variation with time t of the acceleration a of an object (graph attached). What is the change in velocity of the object in the time interval 0 to 4s? Homework Equations a = v/t The Attempt at a Solution My initial answer was -8 m/s, by simply finding the...

Homework Statement Given that ##x=\phi (t)##, ##y=\psi(t)## is a solution to the autonomous system ##\frac{dx}{dt}=F(x,y)##, ##\frac{dy}{dt}=G(x,y)## for ##\alpha < t < \beta##, show that ##x=\Phi(t)=\phi(t-s)##, ##y=\Psi(t)=\psi(t-s)## is a solution for ##\alpha+s<t<\beta+s## for any real...

Hello, I asked this similar questions on a different thread but it may be more appropriate for the chemistry forum. What is the reason we can only measure energy "changes" and not the actual energy value associated with a system? Absolute energies and enthalpy cannot be determined but I am not...

Sorry if this is the wrong subforum i am new here How could one turn Palladium-102 into palladium-103? Would you take a cyclotron and hit it with neutrons? Or would you take Rhodium-103 and hit it with protons? The only reason I ask is because it has a half life of 17 days, and because of that...

Hello Forum, I understand that energy, either kinetic is a relative quantity whose value depends on the frame of reference and its motion. Is that true for potential energy as well? I read on a physics book that only changes in energy can be measure. What does that exactly mean? Why can we...

When we make a symmetrie transformation in a quantum system, the state ##|\psi \rangle## change to ## |\psi' \rangle = U|\psi \rangle##, where ##U## is a unitary or antiunitary operator, and the operator ##A## change to ##A'##. If we require that the expections values of operators don't change...

Cooked some french fries last night using oil saved in the refrigerator. The oil appears to have undergone a phase change, after some time in the refrigerator instead of being a yellowish transparent liquid it was a semi-solid soft whitish non-transparent stuff when I took it out of the...

Homework Statement The assignment is to transform the following differential equation: ##x^2\frac {\partial^2 z} {\partial x^2}-2xy\frac {\partial^2 z} {\partial x\partial y}+y^2\frac {\partial^2 z} {\partial y^2}=0## by changing the variables: ##u=xy~~~~~~y=\frac 1 v##Homework Equations...

Hi. I am currently studying the market for equity options and the use of these to predict stock return around company earnings announcements. The dependent variable in my regression analyses have been the relative change in stock price or log-return from the day before the announcement to...

I've been searching and it seems I am not smart enough to find the solution for this... Let say I have a fully closed box made of concrete left in air. The pressure inside the box is 0.01atm. Since it is left in air, the air will come inside the box through concrete walls(since concrete is...

We all know that the state of matter can be changed by increasing temperature or by applying pressure. And, all of these, in some way lead to a change in the particles' speed. The speed of the particle decides the state of matter. So, if we were to throw an object at very high speeds, like 50%...

Is there a difference between the meaning of charge conjugation in Relativistic Quantum Mechanics and its meaning in Quantum Field Theory? In chapter 4.7.5 of "Thomson Modern Particle Physics" the charge conjugation operator is derived without changing the electromagnetic field Aμ. This...

Hi All, I'm really struggling with the below question - I'm not sure if I've taken the correct approach to determining the model as there may be an easier way to do this? Any help in much appreciated, please let me know if I have submitted this template correctly as this if my first time...

Homework Statement When running, some (heat) energy is lost by the evaporation of sweat. If a runner loses 1.0 MJ( Mega Joules) of energy via sweating, calculate an approximate mass of sweat evaporated from the runner. Homework Equations Q = McΔT Q (Joules) = M (Mass) c (Maximum Heat...

The Earth’s magnetic field is slowly moving with respect to the Earth’s surface and to the Sun’s incoming radiation and solar wind direction. Does the tilting/moving of Earth’s magnetic field axis to the incoming solar wind direction change the protection on different points of the Earth’s...

Is it possible to change a fundamental property of a particle? If that can be done, will it's twin particle's state also be altered accordingly?

Can an expanding balloon be considered a control volume?

hi everyone! i am not into physics, but need it now,i am a programmer workin on an IOT project...so kinda need help. i want to use a capacitor to see what passed between two plates...knowing, it is the change in dielectric after certain intervals...how do i measure the change at the other...

Homework Statement A point charge of 6 × 10−9 C is located at the origin. The magnitude magnitude at ##\langle 0.6,0,0\rangle## m is 150 N/C Next, a short, straight, thin copper wire 5 mm long is placed along the x axis with its center at location ##\langle 0.3,0,0 \rangle## m. What is the...

Homework Statement A 15 kg block is attached to a very light horizontal spring of force constant 5000.0 N/m and is resting on a frictionless table. It is struck by a 3.00 kg stone at 8.00 m/s to the right, then rebounds at 2.00 m/s to the left. Homework Equations ΔE = ΔK + ΔU The Attempt at...

If a reservoir is in thermal contact with a system, why is the entropy simply Q/T ? Shouldn't this equation only valid for reversible process? Why is it reversible?

if I have a pool that is 20x20 surface area and I put a 200 gallon block of ice it, the water level will go up by X amount. when it melts how much will the water level change?

Homework Statement It is necessary to calculate the volume of the coin which has mass 25 kg and how does change its volume when it is necessary to calculate its volume at a depth of 5000m. Compare volume change by pressure with the volume change by pressure with the Volume change by...

What I understood is that The Schwazschild metric is obtained by setting spherical symmetry in the metric and solves the field equation in vacuum. But is the flat metric a solution too, or does it mean that changing the coordinates induces gravity ?

We know that "plastic" and "glass" charges were arbitrarily assigned to be negative and positive respectively, and electrons and protons were given their charges based upon that assignment (According to Randall D. Knight in Physics for Scientists and Engineers). I am curious if any significant...

Hello everyone, Can the mass flow rate of air by a propeller connected to an engine through a small tube change if the rpm of the propeller is increased?

Good day all! I have the following exercise One kilo-mole of air expands adiabatically from an initial state p1=1 bar, T1=340 K to a final state V2= 2V1. Compute the temperature of the final state, for the following cases: Joule expansion (gas free expansion with W12=0) My problem is with the...

Homework Statement 2.Relevant equations[/B]The Attempt at a Solution How does a reversible process in the universe imply the entropy doesn't increase? I understand that the change of entropy in a closed reversible cycle is 0 in the system, but I don't get why a not closed reversible process...

How to get from 14.24 to 14.25?

LB is bisector of triangle ABC. suppose, there is a new triangle that called AED. alpha is a angle between LB to AD that is bisector of AED. The triangles can be on any place in the plane. What the value biggest angle ($$alpha$$) can be?

If a hypothetical planet was once where the asteroid belt is now, and was removed (for example exploded and fell inwards towards the sun where it got burnt up), would this cause the inner planets to migrate outwards into new orbits due to the orbital resonance lost by this hypothetical planet...

We all know that our CO2 emissions will warm the planet. However I am wondering to what extent do climate models include the view that we might be heading to a new Maunder Minimum? https://www.nextbigfuture.com/2018/11/winter-is-coming-super-grand-solar-minimum.html Will this buy us a bit more...

Homework Statement An insulated piston-cylinder device contains 5 L of saturated liquid water at a constant pressure of 150 kPa. An electric resistance heater inside the cylinder is now turned on, and 2200 kJ of energy is transferred to the steam. Determine the entropy change of the water...

Hello! In some of my college Physics practice problems, amplitude of a spring in Simple Harmonic Motion does not change with mass (for example, when the mass splits in 2 at equilibrium in a horizontal oscillator - see picture). But, in other problems, the Vmax of the oscillator remains constant...

1. Homework Statement if a rigid adiabatic container has a fan inside that provides 15000 j of work to an ideal gas inside the container, does the change in entropy would be the same as if 15000 j of heat are provided to the same rigid container (removing the insulation)?2. Relevant equations...

How do the redshift change along the galactic plane or ortoganal to the galactic plane? If we measure a redshift of a star on the backgorund of other side of our galactic plane (where most stars are concentrated) are the redshifts avaraged higher? Is there a study or research discussing this...

Homework Statement Sorry for so many posts lately, hopefully this is allowed. What tangent points on ##g(x)=\frac {12} {x+1}## has an instantaneous rate of change of -3? Homework EquationsThe Attempt at a Solution [/B] I know that once I derive ##g(x)=\frac {12} {x+1}## I can set the...

If you have a particle in a 1-d box with a finite potential when ##0 < x < L ## and an infinite potential outside this region, then the normalised wavefunction used to describe said particle is ## \psi (x) = \sqrt{\frac{2}{L}}\sin(\frac{n\pi x}{L})##. However, if you had say instead a finite...

Engineering has taught us that unequal impedances between feed line and antenna feed point will result in return reflections along the feed line back to the source. The mixing of the forward and reflected waves cause nodes which consist of variations min and max voltages along the line...

Homework Statement Figure 5 shows the input and output wave forms for a proportional plus integral controller. State: (i) the controllers proportional gain (ii) the controllers integral action time The attachment below is a copy and paste of the input and output wave forms I am given...

Suppose I have a velocity field V^a which looks like < \partial x / \partial t , \partial y / \partial t , \partial z / \partial t > and I use the metric tensor to change it into a covector field V_a = g_{ab}V^a. Does it then represent the same quantity or < \partial t / \partial...

In transforming an integral to new coordinates, we multiply the “volume” element by the absolute value of the Jacobian determinant. But in the one dimensional case (where “change of variables” is just “substitution”) we do not take the absolute value of the derivative, we just take the...

Homework Statement Please see attached image for the full scope of the problem, and to see the work drawn out by the text. My question lies with line 3 as it is clear that u-substitution was used on a definite integral, but the limits of integration were not changed. Homework EquationsThe...

Is the equation presented (that the time-derivative of a given vector in such a scenario is equal to its angular frequency vector cross the vector itself) true in the case of a vector whose origin is not on the axis of rotation? The way I'm visualizing this, if we take such a displaced origin...

When an object (e.g. racecar) moves around in circles with constant tangential velocity, constant centripetal acceleration is present. What happens to the centripetal acceleration when the racecar is at rest, then increases its speed? I know that the tangential velocity increases due to the...

Homework Statement How much energy must be removed from the system to turn liquid copper of mass 1.5kg at 1083 degrees celsius to solid copper at 1000 degrees celsius? a. -2.49X10^5J b. -3.67X10^4J c. 2.25X10^3J d. 9.45X10^4J e. -2.78X10^3J Homework Equations Q=Mc(Tf-Ti)...

1. The problem statement. A tennis ball of mass m moving horizontally with speed u strikes a vertical tennis racket. The ball bounces back with horizontal speed v. Homework Equations p = mv The Attempt at a Solution My answer was m(v-u), meaning the final momentum (mv) subtracted from the...

This is an inquiry about some of the details of the bending of the trajectory if a photon by curved space-time (S-T) from the perspective of general relativity (GR). The environment in this scenario contains a black hole at its center, a photon passing by the black hole a km above the event...