Answer:

Explanation:
The magnitude of the electrical force between the two point charges is

where
k is the Coulomb's constant
is the magnitude of each charge
r = 3.00 m is the separation between the two charges
Substituting the numbers into the formula, we find

Answer:
Time, t = 0.87 seconds
Explanation:
Given that,
Initial velocity of the object, u = 4.3 m/s
The coefficient of kinetic friction between horizontal tabletop and the object is 0.5
We need to find the time taken by the object for the object to come to rest i.e. final velocity will be 0.
Using first equation of motion to find it as :

a is the acceleration, here, 


So, the time taken by the object to come at rest is 0.87 seconds. Hence, this is the required solution.
Got shot with a pump shotgun to the head
Electrical energy.................
To solve this problem we will apply the concepts related to the calculation of the speed of sound, the calculation of the Mach number and finally the calculation of the temperature at the front stagnation point. We will calculate the speed in international units as well as the temperature. With these values we will calculate the speed of the sound and the number of Mach. Finally we will calculate the temperature at the front stagnation point.
The altitude is,

And the velocity can be written as,


From the properties of standard atmosphere at altitude z = 20km temperature is



Velocity of sound at this altitude is



Then the Mach number



So front stagnation temperature



Therefore the temperature at its front stagnation point is 689.87K