## Frictional force

(1) What is the coefficient of friction of a 10kg block that reaches 2m / s at a 10m displacement from rest? Since the force that is applied to it is 10N.

*We can calculate the acceleration of the block using the Torricelli equation:*

*By the principle of dynamics, where the resulting force is proportional to mass and acceleration:*

*Knowing the modulus of frictional force it is possible to calculate its coefficient of friction:*

(2) A force F is applied to a block of 15kg that slides over a surface where the coefficient of dynamic friction is 0.25. The body has constant acceleration of 1m / s². What is the force applied to the body?

*By the principle of dynamics:*

## Tensile strength

(1) A spring has elastic constant k = 2.5kN / m. When it is 12cm compressed, how strong will it be?

*By Hooke's Law:*

(2) A body comes into equilibrium when the resulting force on it is zero. Being:

What will the spring deform when the system is in equilibrium?

*When the system is in balance:*

*Then the tensile force will be equal to the Weight Force:*