To solve the problem, it is necessary the concepts related to the definition of area in a sphere, and the proportionality of the counts per second between the two distances.
The area with a certain radius and the number of counts per second is proportional to another with a greater or lesser radius, in other words,


M,m = Counts per second
Our radios are given by



Therefore replacing we have that,






Therefore the number of counts expect at a distance of 20 cm is 19.66cps
Answer:
The increase in the internal energy of the system is 360 Joules.
Explanation:
Given that,
Heat supplied to a system, Q = 292 J
Work done on the system by its surroundings, W = 68 J
We need to find the increase in the internal energy of the system. It can be given by first law of thermodynamics. It is given by :

So, the increase in the internal energy of the system is 360 Joules. Hence, this is the required solution.
Explanation:
Given that,
Initial speed of the bus, u = 0
Acceleration of the bus, a = 0.5 m/s²
Let v is the velocity at the end of 2 minutes. The change in velocity divided by time equals acceleration.
So,

Let d is the distance cover during that time. So,

So, the final speed is 60 m/s and the distance covered during that time is 3600 m.
Answer:
The electric force between them is 878.9 N
Explanation:
Given:
Identical charge
C
Separation between two charges
m
For finding the electrical force,
According to the coulomb's law

Here, force between two balloons are repulsive because both charges are same.
Where 

N
Therefore, the electric force between them is 878.9 N
The answer is (a).
Golf balls have a higher density than water hence sink to the bottom.