Physics, 09.03.2020 20:45 buddyshaw76

A long straight wire has fixed negative charge with a linear charge density of magnitude 3.8 nC/m. The wire is to be enclosed by a coaxial, thin-walled, nonconducting cylindrical shell of radius 1.6 cm. The shell is to have positive charge on its outside surface with a surface charge density σ that makes the net external electric field is zero. Calculate σ.

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Answer from: maddbroms

$\sigma=3.5810\times 10^-^8C/m^2$

Explanation:

1. We need two market $\sigma$ for the cylindrical shell and second for the rod.

By Gauss Law for shell, $\epsilon \int E.dA=q_e_n_c$ and $q_e_n_c=\sigma A$ then eq. becomes $\epsilon \int E.dA=A$ , we integrate to find

$\epsilon E=\sigma$ .... eqtn 1

Gauss Law for rod, $\epsilon \int E.dA=\lambda L$ Where $\lambda$ is charge per length and is the rod's length ( $q_e_n_c=\lambda L$ ). We integrate to find

$\epsilon E=-\frac{\lamda L}{2\pi RL}.....eqtn2$

-solve the two equations to find the value of $\sigma$

$-\frac{\lambda}{2\pi R}=\sigma\\\frac{3.8\times 10^-^9C/m}{2\times \pi \times 1.6\times 10^-^2}\\\sigma=3.5810\times 10^-^8C/m^2$

Answer from: Quest

force is based upon mass and acceleration.the statement is not always true.

it can be explained from newton's second law of motion.

as per newton's second law of motion the rate of change of momentum is directly proportional to the applied force and takes place along the direction of force.

mathematically it can be written as -

$f\alpha \frac{dp}{dt}$

⇒ $f= k \frac{dp}{dt}$

here k is the proportionality constant whose value is 1.

$f=\frac{dp}{dt}$

$f= \frac{d[mv]}{dt}$

$f= m\frac{dv}{dt} +v\frac{dm}{dt}$

$f=ma+v\frac{dm}{dt}$ [a is the acceleration=dv/dt]

hence we see that force not only depends on mass and acceleration but also on velocity and rate of change of mass. force f will depend on mass and acceleration only when mass is constant.

hence the statement that force is based upon mass and acceleration is false.

Answer from: Quest

Answer (d) valerie rides her bike south at 8 kilometers per hour///owen jogs south at 8 kilometers per hour ;

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A long straight wire has fixed negative charge with a linear charge density of magnitude 3.8 nC/m. T...

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