Place an eraser on the ruler. Start lifting the ruler at one end. Measure the angle at which the eraser starts to slide along the ruler.

Place an eraser on the ruler. Start lifting the ruler at one end. Measure the angle at which the eraser starts to slide along the ruler. Prove that the tangent of this angle is equal to the coefficient of friction: tga = u

The eraser will begin to slide along the ruler at an angle of 63 °.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.