When the positive and negative charges grow large enough, a giant spark, lightning, occurs between the two charges within the cloud.
Answer
The rate at which the magnetic field is changing is
Explanation
From the question we are told that
The electric field strength is 
The radius is 
The rate of change of the magnetic field is mathematically represented as

Where
is change of a unit length

Where A is the area which is mathematically represented as

So
where L is the circumference of the circle which is mathematically represented as

So
![E (2 \pi r ) = (\pi r^2 ) [\frac{dB}{dt} ]](https://tex.z-dn.net/?f=E%20%282%20%5Cpi%20r%20%29%20%3D%20%20%28%5Cpi%20r%5E2%20%29%20%5B%5Cfrac%7BdB%7D%7Bdt%7D%20%5D)
![E = \frac{r}{2} [\frac{dB}{dt} ]](https://tex.z-dn.net/?f=E%20%20%3D%20%20%20%5Cfrac%7Br%7D%7B2%7D%20%20%5B%5Cfrac%7BdB%7D%7Bdt%7D%20%5D)
![[\frac{dB}{dt} ] = \frac{E}{ \frac{r}{2} }](https://tex.z-dn.net/?f=%5B%5Cfrac%7BdB%7D%7Bdt%7D%20%5D%20%3D%20%5Cfrac%7BE%7D%7B%20%5Cfrac%7Br%7D%7B2%7D%20%7D)
substituting values
![[\frac{dB}{dt} ] = \frac{3.5 *10^{-3}}{ \frac{15}{2} }](https://tex.z-dn.net/?f=%5B%5Cfrac%7BdB%7D%7Bdt%7D%20%5D%20%3D%20%5Cfrac%7B3.5%20%2A10%5E%7B-3%7D%7D%7B%20%5Cfrac%7B15%7D%7B2%7D%20%7D)
1. 2+0.5+2.5= 3. 2km/hr average
2. 14-6=4seconds. 8m/s in 4s = 2m/s acceleration
3. 15m/s divided by 2.5 = 6m/s acceleration
The Density of this Rectangular Prism would be 7.5, since the Volume of the Rectangular Prism can be determined by using the formula: length times width times height.
5*2*4, or 2*4*5, or 5*4*2= 40, because 5*2= 10, and 10*4= 40.
The Problem hereby, states that the mass of the Rectangular Prism is 300 grams, right?
Since the Formula for calculating the Density of an Object is Mass divided by Volume, 300 divided by 40 gives you 7.5, and we wouldn't make the answer 7.5 cubed, or 7.5 squared, or 7.5 grams cubed, or 7.5 grams squared, since squared would be for finding only the Area for 2-D Shapes, and cubed would be for finding only the Volume for 3-D Shapes, but in this case that we had here, We were finding Density, which includes Mass AND Volume, not just Volume.