A boy sliding down a frictionless plane inclined at an angles 35° with the horizontal. What is the acceleration of the book?

Answer 1

force of gravity down the slide:
mg*SinTheta

Forcedowntheslide=mass*acceleration

solve for acceleration.

If you had friction, the force of friction would be mu*mg*CosTheta, and that would subtract from the gravity force down the slide. Frictionless implies mu=0