Answer:
The frictional force
6.446 N
The acceleration of the block a = 6.04 
Explanation:
Mass of the block = 3.9 kg
°
= 0.22
(a). The frictional force is given by


3.9 × 9.81 × 
29.3 N
Therefore the frictional force
0.22 × 29.3
6.446 N
(b). Block acceleration is given by

F = 30 N
= 6.446 N
= 30 - 6.446
= 23.554 N
The net force acting on the block is given by

23.554 = 3.9 × a
a = 6.04 
This is the acceleration of the block.
To solve this problem it is necessary to apply the concepts related to the Stefan-Boltzman law that is responsible for calculating radioactive energy.
Mathematically this expression can be given as

Where
A = Surface area of the Object
Stefan-Boltzmann constant
e = Emissivity
T = Temperature (Kelvin)
Our values are given as





Replacing at our equation and solving to find the temperature 1 we have,




Therefore the the temperature of the coldest room in which this person could stand and not experience a drop in body temperature is 12°C
According to wikipedia <em>a mid-ocean ridge is an underwater mountains system formed by tectonic plates.
</em>Happy studying!<em>
</em>