# Search results

1. ### B Confused about the ideal gas law

You might try this. p(1)V(1) = n(1)RT(1) and p(2)V(2) = n(2)RT(2) and V(1) = V(2) and n(1) = n(2). Divide eqn, 2 by eqn. 1 and solve for T(2).
2. ### B Thermionic emission and current density

What you are describing here is close to what we called thermionic energy conversion in the 1960's. The object was to place two electrodes in close proximity, heat one of them until thermionic electron emission occurs. The electrons with sufficient kinetic energy could cross the gap and be...
3. ### I Direction of the magnetic field of the Earth

This just in from the morning newspaper. The Earth's magnetic field intensity is weakening and magnetic North is moving towards Siberia at 34 miles/year. All of which makes a case for relying on GPS rather than compasses.
4. ### B How is momentum conserved if you lose kinetic energy?

One of my favorite demonstrations in Mechanics is to take two carts of identical mass on a track with velcro affixed to their front bumpers and give them equal and opposite velocities. The system of two carts thus have zero momentum before colliding and stopping in the middle of the track. The...
5. ### Chernobyl and steam explosions

Consider a pressure cooker. As heat is added to the constant volume of the cooker, the liquid water is converted to vapor increasing the pressure which increases the boiling temperature which further increases the pressure until the pressure relief valve is opened, releasing some vapor and...
6. ### Am I looking at the right Physics textbook?

On a scale of 1 to 10, I would give Young and Freedman a 7. This text was formerly Sears and Zemansky, a standard text, and was inherited by Young. The first several editions published under his name were replete with errors. Maybe it has been cleaned up by now. One can only hope. Good luck.
7. ### I How does the pressure drop as a fluid flows through a pipe

The velocity profile across the pipe transitions from uniform at the entrance to about parabolic further downstream. To determine the total pressure, you need to integrate across the velocity profile.
8. ### DIY vacuum chamber advice

If you are going to use a metal base plate, you can drill and tap your base plate for the pipe thread of a spark plug and use glyptal to seal the threads. Spark plugs make great high voltage feedthroughs. We made some simple vacuum systems with thick-walled, one foot ID glass cylinders and...
9. ### A Probability at a temperature T that a system has a particular energy

p ~ exp(-E/kT), E ~ omega^2
10. ### DIY vacuum chamber advice

I did a lot of thermionic emission experiments in high vacuum during the 60's and even built a glass vacuum system tied to a LN cold trap, diffusion pump, and fore pump and an oven to bake and outgas the glass components. Temperatures were measured with an optical pyrometer and W-Re TC's...
11. ### I Error propagation and standard deviation

You might check Kline and McClintock's 1953 paper on uncertainty analysis. It is a standard in the field.
12. ### Am I looking at the right Physics textbook?

All the above comments are good advice. I have a four foot stack of introductory Physics texts we have used over the last 30 years. My favorite is Serway which is used by many universities. The introductory calculus-based courses are usually a total of nine credit hours spread over two or...
13. ### Tangential Acceleration/Tension

srekai: Your solution is correct. v^2 / rg is in fact dimensionless.
14. ### Shooting distance

Your methodology looks OK but 1) the moment of inertia of a rod about one end is mL^2 / 3 and the moment of inertia of the rock is ML^2; 2) the potential energy of the lever and rock in the vertical position is mgL/2 + MgL. Make those changes and recalculate the distance and I'll let you know...
15. ### Why don't voltages add up numerically in an LCR AC circuit?

The best way to see this is to connect an oscilloscope across each element. The differences in phase will be apparent.
16. ### Having a problem in steps while solving integrals

Your LHS (2/3) k^2 x^(3/2) is OK the RHS as you have corrected is v^2 / 2 with an upper limit of 2u and a lower limit of u.
17. ### Having a problem in steps while solving integrals

The slide is wrong in that x is not constant, k is constant. Your formulation is correct up to ∫ v dv as pointed out by haruspex.
18. ### Electric Potential Difference Problem

So you calculate the potential at X due to both the charge at A and the charge at B. Do the same calculation at Y. You can then readily see the difference in potential between points X and Y.
19. ### Electric Potential Difference Problem

Is this a 1D problem or a 2D problem? You need to draw a sketch of the locations under consideration.
20. ### Having a problem in steps while solving integrals

∫ dt = t + C or ∫ dt = Δt
21. ### Car test, and vibrations problem

Case 1 corresponds to shocks which are worn out and if driven over a road with a periodic contour could result in a loss of control. I experienced this on the old bridge across Biloxi Bay which was later destroyed by Katrina. Case 2 represents shocks with a bit of wear. Case 3 is a case of...
22. ### Help me understand the equation V = u + delt v

Δv = ∫ dv = ∫ a dt
23. ### Gravitational Potential Energy Project Thor

The potential energy is -GMm/r and the kinetic energy is GMm/2r so the total energy is -GMm/2r which is the energy required to leave an orbit and escape from the Earth's gravitational well to where the total energy is zero. To get an object to fall to the Earth, you would have to kill its...
24. ### Two lenses. Find the image.

Two thin lenses in contact are equivalent to a single thin lens whose focal length is given by 1/f = 1/f1 + 1/f2. (Serway). Then 1/i = 1/f - 1/o as usual.
25. ### Pitot tube

This is not that complicated. The total pressure in the Pitot tube is q + p(static) and p(static) = ρgh + p(atmospheric). The conversion factor is 406 inches water = 1 atmosphere = 101.3 kPa. U(m/s) = √2q(n/m^2) / ρ(kg/m^3) The sensitivity of the Pitot tube to crossflow is of course...
26. ### Pitot tube

Measurement of fluid velocity with a Pitot tube is based on Bernoulli's equation which represents the conservation of energy per unit volume of fluid flow. p(total), pt, represents the total energy; p(static), ps, represents the potential energy: and q = ρU^2 / 2 = dynamic pressure...
27. ### Finding the Final Velocity

If you have studied the conservation of energy, this is a good application. The initial potential energy, mgh, equals the final kinetic energy, mv^2/2 plus the work done against friction, μ mg cos θ x.
28. ### Finding the Final Velocity

In the absence of friction the acceleration will be g sin θ, however if this is a block and not a cart with only rolling friction, then the acceleration of the block will be g (sin θ - μ cos θ) provided of course that tan θ > μ. Thirty years ago we used air tracks, gliders, and timers but now...

See #7 & #8.
30. ### Find the change in the Kinetic energy of an Ideal Gas

That is what it looks like to me.