I am new in the forum; and I am currently studying physics at the high school level. I have a little problem... and I would greatly appreciate any help that you could provide me;

The thing is; I have to do an investigation on the relationship between magnetic flux density and temperature. My hypothesis is that when a ferromagnet is heated, the magnitude of B should decrease. However, I can't seem to find any formula which relates magnetic flux density and temperature, at least

If the speed of a 62 kg skier at P is 1.5 m/s, and the conversion from potential energy to kinetic energy as she skies down the hill is 65% efficient, then her speed at point Q will be _ m/s and _ kJ of energy will have been lost due to friction.

I found the speed and it was 11.57 m/s. However, I don't get the same answer as the answer key says for the kJ of energy lost due to friction. The answer was 2.6 kJ, but I keep getting 3.6 kJ. What I did was I did epi+eki= ekf + epf + heat. Isolated heat to find the energy lost due to friction. I used the speed, 11.57m/s for the ekf. I still keep getting 3.6kJ and not 2.6 at all. ]]>

So with more energy there are more possible arrangement of the molecules so entropy is more.

Does this mean as an object gets hotter there are more ways molecules can be arranged? Is entropy the number of arrangements of a molecule? ]]>

In the beginning for a couple of days when i wore the glasses, nearby objects like the floor or steps appeared to be further away when viewed through these glasses. So in the very beginning it was difficult to judge the actual position of the steps. They appeared further away. But now I have got used to it so it is not a problem.

So as per my knowledge when an image is moved closer to a concave mirror it appears further away (Virtual Property). Is this property of concave mirror responsible for this situation where the floor or steps appeared to be further away? ]]>

I am using molecular dynamics to calculate energy for ionic liquid. In the article that is proposed equation of state that I want to use, the author would call the energy in the following formula(u) conformational(potential energy):

(du/dv)T + T(dp/dT)V = ptot

But the other article would call it total internal energy which means total energy in the thermodynamic system.

As you know MD can produce potential energy and total energy, which one should I use for the above formula?

Best ]]>

When a ball reaches its maximum height, its speed is one-fourth the speed with which it was thrown. What was the launch angle?

I understand that at the maximum height, the velocity of the ball only has a component in the x-direction, and I've made the distinction that the x-component of the velocity must be 1/4 the launch velocity, Vo. I did some "guess and check" work and got that the angle would be about 75.5, but I have no idea how to prove that mathematically.

Attachment 2030

$\displaystyle Vix=\sqrt{Vix^2+viy^2}/4$

$\displaystyle 4Vix=\sqrt{Vix^2+viy^2}$

$\displaystyle 16Vix^2=Vix^2+Viy^2$

$\displaystyle 15Vix^2=Viy^2$

$\displaystyle Arctan(15/4)=75.1 degrees$

t=1:0.1:6;

x1=sin(2*pi*t);

x2=sin(3*pi*t);

I can easily see the differential beating envelope but no clue how the average combined frequencey is reflected on the graph – e,g, when I count the zero crossings I rather get the higher of the two component frequencies,

Regards, Pawel

So does that mean kinetic energy = potential energy when the object is at rest? This has to be the case if law of conservation of energy is true. Since at rest kinetic energy is 0 and during motion potential energy is 0. ]]>

A long string is wrapped around a 5.00-cm-diameter cylinder, initially at rest, that is free to rotate on an axle.

The string is then pulled with a constant acceleration of 1.50 m/s2 until 1.25 m of string has been unwound.

Assume the string unwinds without slipping.

(a) What is the angular displacement of the cylinder after 1.25 m of string has been unwound?

(b) What is the angular acceleration of the cylinder as the string is unwound?

(c) What is the final angular velocity of the cylinder, expressed in rpm?

tangential acceleration(at) =1.25m/s

arc length(s)=1.25m

radius of the cylinder(r) = .025m

a.)

Θ=s/r

Θ=1.25/.025

Θ=50 radians

b.)

at=αr

1.25=α(.025)

1.25/.025=α

a=60 radians/sec^2

c.)

Using the equation wf=wi+2αΘ

wf=2αΘ

wf=2(60)(50)

wf=6000rads/second

This is where I am stuck. I'm not really quite sure if my reasoning that the tangential acceleration is 1.25m/s^2, or if my final angular velocity is reasonable at all. I'm also having trouble wrapping my head around the conversion to RPM. Thanks for any help in advance. ]]>

So far, I finished 1, 2, and 4. However, I am stuck with Q3. How do I solve it? I really have no idea where to start. It's just a wire bend to form a right triangle.

Any help would be appreciated!

]]>

For the F=ma, I manipulated the equation and have gotten, a=190N/78kg=2.4 or would the formula be W=ma, hence, 78kg/190N=0.410 is this correct? And how do I solve the other portion of the problem? ]]>

If we interpret this formula then as we know E= potential energy + kinetic energy. 1/2 mv2 gives us kinetic energy. So mc2 must be potential energy if the formula is correct.

Is this right? ]]>

I want to calculate thermodynamical properties of my molecule which I am calculating its thermodynamical properties of non-ideal part using Molecular dynamics. I need ideal gas state total energy, Cp, and Cv in several different temperatures. I am using opt+freq at B3lyp/6-311++G(d,p) setting to calculate thermochemistry properties. I am using gaussian 09, and I have some question, and I will be really grateful for your answers:

1- I would control temperature, but do you think I should change the pressure from its default (=1) to zero(or near zero) because of enforcing ideal situation, or it is not important in Ab initio simulation?

2- I need energy, Cp, and Cv. Thermochemistry part of frequency has total thermal energy, Cp, and Cv. Do you think I should use this total energy as my molecule calculations ideal part or the total energy in HF at the near of the end of output file of gaussian? How about Cp and Cv? If the energy should not be taken from thermochemistry part(why?) how can I use Cp and Cv there?

Best regards ]]>