The electric potential is a scalar unit, so we don't have to struggle with the vectors. The formula that gives electric potential is
![V = \frac{1}{4\pi\epsilon_0}\frac{q}{r}](https://tex.z-dn.net/?f=V%20%3D%20%5Cfrac%7B1%7D%7B4%5Cpi%5Cepsilon_0%7D%5Cfrac%7Bq%7D%7Br%7D)
1) At point a, the electric potential is the sum of the potentials due to q1 and q2. So,
![V_a = \frac{1}{4\pi\epsilon_0}\frac{q_1}{r_1} + \frac{1}{4\pi\epsilon_0}\frac{q_2}{r_2}](https://tex.z-dn.net/?f=V_a%20%3D%20%5Cfrac%7B1%7D%7B4%5Cpi%5Cepsilon_0%7D%5Cfrac%7Bq_1%7D%7Br_1%7D%20%2B%20%5Cfrac%7B1%7D%7B4%5Cpi%5Cepsilon_0%7D%5Cfrac%7Bq_2%7D%7Br_2%7D)
The distance from the center of the square to one of the corners is ![\sqrt2 L/2 = 0.035m](https://tex.z-dn.net/?f=%5Csqrt2%20L%2F2%20%3D%200.035m)
![V_a = \frac{1}{4\pi\epsilon_0}\frac{2\times10^{-6}}{0.035} + \frac{1}{4\pi\epsilon_0}\frac{-2\times10^{-6}}{0.035} = 0](https://tex.z-dn.net/?f=V_a%20%3D%20%5Cfrac%7B1%7D%7B4%5Cpi%5Cepsilon_0%7D%5Cfrac%7B2%5Ctimes10%5E%7B-6%7D%7D%7B0.035%7D%20%2B%20%5Cfrac%7B1%7D%7B4%5Cpi%5Cepsilon_0%7D%5Cfrac%7B-2%5Ctimes10%5E%7B-6%7D%7D%7B0.035%7D%20%3D%200)
The answer is zero, because the point charges are at equal distances and their magnitudes are also equal but their directions are opposite.
2) ![V_b = \frac{1}{4\pi\epsilon_0}\frac{q_1}{r_1} + \frac{1}{4\pi\epsilon_0}\frac{q_2}{r_2}](https://tex.z-dn.net/?f=V_b%20%3D%20%5Cfrac%7B1%7D%7B4%5Cpi%5Cepsilon_0%7D%5Cfrac%7Bq_1%7D%7Br_1%7D%20%2B%20%5Cfrac%7B1%7D%7B4%5Cpi%5Cepsilon_0%7D%5Cfrac%7Bq_2%7D%7Br_2%7D)
![r_1 = 0.05\sqrt2m\\r_2 = 0.05m](https://tex.z-dn.net/?f=r_1%20%3D%200.05%5Csqrt2m%5C%5Cr_2%20%3D%200.05m)
![V_b = \frac{1}{4\pi\epsilon_0}\frac{2\times10^{-6}}{0.05\sqrt2} + \frac{1}{4\pi\epsilon_0}\frac{-2\times10^{-6}}{0.05}\\V_b = \frac{1}{4\pi\epsilon_0}\frac{2\times10^{-6}}{0.05} (\frac{1}{\sqrt2}-1)\\V_b = \frac{1}{4\pi\epsilon_0} (4\times 10^{-5})(-0.29)\\V_b = (-\frac{2.9\times10^{-6}}{\pi\epsilon_0})[tex]3) The work done on q3 by q1 and q2 is equal to the difference between energies. This is the work-energy theorem. So,[tex]W = U_b - U_a](https://tex.z-dn.net/?f=V_b%20%3D%20%5Cfrac%7B1%7D%7B4%5Cpi%5Cepsilon_0%7D%5Cfrac%7B2%5Ctimes10%5E%7B-6%7D%7D%7B0.05%5Csqrt2%7D%20%2B%20%5Cfrac%7B1%7D%7B4%5Cpi%5Cepsilon_0%7D%5Cfrac%7B-2%5Ctimes10%5E%7B-6%7D%7D%7B0.05%7D%5C%5CV_b%20%3D%20%5Cfrac%7B1%7D%7B4%5Cpi%5Cepsilon_0%7D%5Cfrac%7B2%5Ctimes10%5E%7B-6%7D%7D%7B0.05%7D%20%28%5Cfrac%7B1%7D%7B%5Csqrt2%7D-1%29%5C%5CV_b%20%3D%20%5Cfrac%7B1%7D%7B4%5Cpi%5Cepsilon_0%7D%20%284%5Ctimes%2010%5E%7B-5%7D%29%28-0.29%29%5C%5CV_b%20%3D%20%28-%5Cfrac%7B2.9%5Ctimes10%5E%7B-6%7D%7D%7B%5Cpi%5Cepsilon_0%7D%29%5Btex%5D%3C%2Fp%3E%3Cp%3E%3C%2Fp%3E%3Cp%3E3%29%20The%20work%20done%20on%20q3%20by%20q1%20and%20q2%20is%20equal%20to%20the%20difference%20between%20%20energies.%20This%20is%20the%20work-energy%20theorem.%20So%2C%3C%2Fp%3E%3Cp%3E%5Btex%5DW%20%3D%20U_b%20-%20U_a)
![U = \frac{1}{4\pi\epsilon_0}\frac{q_1q_3}{r} = Vq_3](https://tex.z-dn.net/?f=U%20%3D%20%5Cfrac%7B1%7D%7B4%5Cpi%5Cepsilon_0%7D%5Cfrac%7Bq_1q_3%7D%7Br%7D%20%3D%20Vq_3)
![W = q_3(V_b - V_a) = q_3(V_b - 0)\\W = (-2\times10^{-6})(-\frac{2.9\times10^{-6}}{\pi\epsilon_0})\\W = \frac{5.8\times10^{-12}}{\pi\epsilon_0}](https://tex.z-dn.net/?f=W%20%3D%20q_3%28V_b%20-%20V_a%29%20%3D%20q_3%28V_b%20-%200%29%5C%5CW%20%3D%20%28-2%5Ctimes10%5E%7B-6%7D%29%28-%5Cfrac%7B2.9%5Ctimes10%5E%7B-6%7D%7D%7B%5Cpi%5Cepsilon_0%7D%29%5C%5CW%20%3D%20%5Cfrac%7B5.8%5Ctimes10%5E%7B-12%7D%7D%7B%5Cpi%5Cepsilon_0%7D)
Answer:
Explanation:
F=kx
x=F/k
F=2000 kg
x=100 cm=9*10^-3
effective spring constant=k=F/x
k=2000/9*10^-3=2.2*10^-5
now frequency
f=1/2π√k/m
f=1/2*3.14√2.2*10^-5/310
f=1/6.28√7.097*10^-8
f=1/6.28*2.7*10^-4
f=0.16*2.7*10^-4
f=4.32*10^-5
Given,
Radius of curvature of concave mirror = 1.6m
We know that ,
Focal length = radius/2
Hence ,
Focal length of concave mirror = radius of concave mirror /2
=> F = 1.6/2
=> F = 0.8m
Hence the focal length of concave mirror is 0.8 m
Answer:
![5.94\ \text{m/s}](https://tex.z-dn.net/?f=5.94%5C%20%5Ctext%7Bm%2Fs%7D)
![1.7](https://tex.z-dn.net/?f=1.7)
![0.577](https://tex.z-dn.net/?f=0.577)
Explanation:
g = Acceleration due to gravity = ![9.81\ \text{m/s}^2](https://tex.z-dn.net/?f=9.81%5C%20%5Ctext%7Bm%2Fs%7D%5E2)
= Angle of slope = ![30^{\circ}](https://tex.z-dn.net/?f=30%5E%7B%5Ccirc%7D)
v = Velocity of child at the bottom of the slide
= Coefficient of kinetic friction
= Coefficient of static friction
h = Height of slope = 1.8 m
The energy balance of the system is given by
![mgh=\dfrac{1}{2}mv^2\\\Rightarrow v=\sqrt{2gh}\\\Rightarrow v=\sqrt{2\times 9.81\times 1.8}\\\Rightarrow v=5.94\ \text{m/s}](https://tex.z-dn.net/?f=mgh%3D%5Cdfrac%7B1%7D%7B2%7Dmv%5E2%5C%5C%5CRightarrow%20v%3D%5Csqrt%7B2gh%7D%5C%5C%5CRightarrow%20v%3D%5Csqrt%7B2%5Ctimes%209.81%5Ctimes%201.8%7D%5C%5C%5CRightarrow%20v%3D5.94%5C%20%5Ctext%7Bm%2Fs%7D)
The speed of the child at the bottom of the slide is ![5.94\ \text{m/s}](https://tex.z-dn.net/?f=5.94%5C%20%5Ctext%7Bm%2Fs%7D)
Length of the slide is given by
![l=h\sin\theta\\\Rightarrow l=1.8\sin30^{\circ}\\\Rightarrow l=0.9\ \text{m}](https://tex.z-dn.net/?f=l%3Dh%5Csin%5Ctheta%5C%5C%5CRightarrow%20l%3D1.8%5Csin30%5E%7B%5Ccirc%7D%5C%5C%5CRightarrow%20l%3D0.9%5C%20%5Ctext%7Bm%7D)
![v=\dfrac{1}{2}\times5.94\\\Rightarrow v=2.97\ \text{m/s}](https://tex.z-dn.net/?f=v%3D%5Cdfrac%7B1%7D%7B2%7D%5Ctimes5.94%5C%5C%5CRightarrow%20v%3D2.97%5C%20%5Ctext%7Bm%2Fs%7D)
The force energy balance of the system is given by
![mgh=\dfrac{1}{2}mv^2+\mu_kmg\cos\theta l\\\Rightarrow \mu_k=\dfrac{gh-\dfrac{1}{2}v^2}{gl\cos\theta}\\\Rightarrow \mu_k=\dfrac{9.81\times 1.8-\dfrac{1}{2}\times 2.97^2}{9.81\times 0.9\cos30^{\circ}}\\\Rightarrow \mu_k=1.73](https://tex.z-dn.net/?f=mgh%3D%5Cdfrac%7B1%7D%7B2%7Dmv%5E2%2B%5Cmu_kmg%5Ccos%5Ctheta%20l%5C%5C%5CRightarrow%20%5Cmu_k%3D%5Cdfrac%7Bgh-%5Cdfrac%7B1%7D%7B2%7Dv%5E2%7D%7Bgl%5Ccos%5Ctheta%7D%5C%5C%5CRightarrow%20%5Cmu_k%3D%5Cdfrac%7B9.81%5Ctimes%201.8-%5Cdfrac%7B1%7D%7B2%7D%5Ctimes%202.97%5E2%7D%7B9.81%5Ctimes%200.9%5Ccos30%5E%7B%5Ccirc%7D%7D%5C%5C%5CRightarrow%20%5Cmu_k%3D1.73)
The coefficient of kinetic friction is
.
For static friction
![\mu_s\geq\tan30^{\circ}\\\Rightarrow \mu_s\geq0.577](https://tex.z-dn.net/?f=%5Cmu_s%5Cgeq%5Ctan30%5E%7B%5Ccirc%7D%5C%5C%5CRightarrow%20%5Cmu_s%5Cgeq0.577)
So, the minimum possible value for the coefficient of static friction is
.