Answer :
The angle at which the eraser first start to slide when the student begins to tilt the book is 32 degrees.
What is friction?
Friction is the force which resist the motion of a body, when the body is in contact with another body or surface.
The friction force of a body is the product of normal force acting on the body and the coefficient of the friction of that body. It can be given as,
[tex]F_f=\mu F_n[/tex]
Here, [tex]F_n[/tex] is the normal force and [tex]\mu[/tex] is the coefficient of the friction.
When the eraser starts to slide, the tangent of the angle of inclination of the book is equal to the coefficient of friction between leather and rubber. This can be given as,
[tex]tan(\theta)=\mu[/tex]
The coefficient of friction between leather and rubber is 0.61. Put this value in the above expression as,
[tex]tan(\theta)=0.61\\\theta=\tan^{-1}(0.61)\\\theta=31.3832\\\theta\cong32^o[/tex]
Hence, the angle at which the eraser first start to slide when the student begins to tilt the book is 32 degrees.
Learn more friction force here;
https://brainly.com/question/13680415