Hello can you retype this question so I can help you?
To solve the exercise it is necessary to apply the concepts related to Newton's Second Law, as well as the definition of Weight and Friction Force.
According to the problem there is a movement in the body and it is necessary to make a sum of forces on it, so that

There are two forces acting on the body, the Force that is pushing and the opposing force that is that of friction, that is

To find the required force then,

By definition we know that the friction force is equal to the multiplication between the friction coefficient and the weight, that is to say





Therefore the horizontal force applied on the block is B) 230N
The answer is D I’m not really sure yet
Yes this is true this causes day and night
The maximum allowable torque must correspond to the allowable shear stress for maximization. To solve this, we use the torsion formula:
Max. Allowable Shear Stress = Maximum Torque ÷ Cross-Sectional Area
8 x 10^6 Pa = Maximum Torque ÷ pi*(d/2)²
Maximum Torque = 8 x 10^6 Pa * pi*(0.06/2)² m²
Maximum Torque = 22,619.47 J or
Maximum Torque = 22.62 kJ
As for the second question, I have no reference figure so I am unable to answer it. I hope I was still able to help you, though.