# Search results for query: *

1. ### I Isn't the force calculated twice?

Isn't the force calculated twice here? For example, the force along AB is at first calculated for the resultant force along OB, then for the resultant force along AC. I think the compression and tensile stress should be ##\frac{F}{2a}##.
2. ### B Adiabatic but permeable piston

How can a permeable piston be adiabatic? If substances can go in and out of the cylinder and the substances have heat energy, heat can be exchanged through a permeable piston. I came across this term in the book, but cannot understand.
3. ### I Can internal energy be calculated from equation of state?

Thanks. That's exactly what I wanted to know.
4. ### I Can internal energy be calculated from equation of state?

We know, $$dU=TdS-PdV$$ ##\int PdV## can be calculated if the equation of state is given. I tried to express ##S## as a function of ##P ,V## or ##T## (any two of those). $$dS=\left(\frac{\partial S}{\partial V}\right)_T dV+\left(\frac{\partial S}{\partial T}\right)_V dT$$ =\left(\frac{\partial...
5. ### I Physical significance of integral of F cross dr

That was not my point. ##d \vec r## represents infinitesimal change in position vector, while ##\vec r## represents position vector. Could you please give me a practical example where the net torque is calculated by ##\int \vec F \times d \vec r## ?
6. ### I Physical significance of integral of F cross dr

Isn't torque defined as ##\vec r \times \vec F## ?
7. ### I Physical significance of integral of F cross dr

In the vector calculus course, I calculated integrals like, ##\int \vec F \times \vec{dr} ## Does this kind of integrals have physical significance or practical application other than Biot-Savart's Law?
8. ### Wye-Delta transformation

To prove the wye-delta transformation formula, it is said 'If the two circuits are to be equivalent, the total resistance between any two terminals must be the same.' But why ? I can't convince myself that it is sufficient condition for the equivalence of circuits.
9. ### Physical significance of an equation of wave

We can mathematically derive the equation of wave, \frac{\partial^2 y}{\partial t^2} = v^2 \frac{\partial^2 y}{\partial x^2}, where v is the velocity of wave propagation. Can we prove this equation physically (not just taking derivatives of the equation of wave, but making physical meaning in...