D. lenses focus light , mirrors do not
1) First of all, we need to find the distance between the two charges. Their distance on the xy plane is
![d= \sqrt{(x_1-x_2)^2+(y_1-y_2)^2}](https://tex.z-dn.net/?f=d%3D%20%5Csqrt%7B%28x_1-x_2%29%5E2%2B%28y_1-y_2%29%5E2%7D%20)
substituting the coordinates of the two charges, we get
![d= \sqrt{(3.5+2)^2+(0.5-1.5)^2}=5.6~cm=0.056~m](https://tex.z-dn.net/?f=d%3D%20%5Csqrt%7B%283.5%2B2%29%5E2%2B%280.5-1.5%29%5E2%7D%3D5.6~cm%3D0.056~m%20)
2) Then, we can calculate the electrostatic force between the two charges
![q_1](https://tex.z-dn.net/?f=q_1)
and
![q_2](https://tex.z-dn.net/?f=q_2)
, which is given by
![F=k_e \frac{q_1 q_2}{d^2}](https://tex.z-dn.net/?f=F%3Dk_e%20%20%5Cfrac%7Bq_1%20q_2%7D%7Bd%5E2%7D%20)
where
![k_e=8.99\cdot10^{9} Nm^2C^{-2}](https://tex.z-dn.net/?f=k_e%3D8.99%5Ccdot10%5E%7B9%7D%20Nm%5E2C%5E%7B-2%7D)
is the Coulomb's constant.
Substituting numbers, we get
![F=8.99\cdot10^{9} Nm^2C^{-2} \frac{(3.3\cdot10^{-6}~C) (-4\cdot10^{-6}~C)}{(0.056~m)^2} =-37.8~N](https://tex.z-dn.net/?f=F%3D8.99%5Ccdot10%5E%7B9%7D%20Nm%5E2C%5E%7B-2%7D%20%20%5Cfrac%7B%283.3%5Ccdot10%5E%7B-6%7D~C%29%20%28-4%5Ccdot10%5E%7B-6%7D~C%29%7D%7B%280.056~m%29%5E2%7D%20%3D-37.8~N)
and the negative sign means the force between the two charges is attractive, because the two charges have opposite sign.
working...
Sound wave needs medium to travel
as energy which travels in this wave is because of transfer from one particle to another particle
If there is no medium then energy can not be transferred and sound wave will not travel
so in vacuum we can not listen sound
similarly here air is removed it means there is no medium inside the jar to travel the sound and hence we can not hear it
Option B is correct
Without air, the sound waves cannot travel to the ear.
Answer:
what do you mean by this?
Explanation: