In physics, power is defined as energy per unit time. You will also hear it described as work per unit time. The standard unit of measure for power is the watt, where a watt is defined as joules (energy) per second (time). This is expressed as a fraction as J/s. If you wanted to increase the power in any operation, you can either increase the energy (more joules) or reduce the time (fewer seconds).
The suns gravitational pull
If we compare the energy of visible light to the energy of X-rays, we find that X-rays have a much higher frequency. Usually, electromagnetic radiation with higher frequency (energy) have a higher degree of penetration than those with low frequency.
Answer:
The potential energy when it reads 40 N is 
Explanation:
From the question we are told that
The lowest reading of the spring balance is 0 N and this is at 0 cm = 0 m
The height reading of the spring balance is 60 N and this is at 20 cm = 0.20 m
Generally the length corresponding to the reading of 40 N is mathematically represented as

=> 
Generally the potential energy is mathematically represented as

Here
So

=> 