A 2.0 kg-book is at rest on a frictionless horizontal floor. You are applying a 10 N downward force, on the book, at an angle of 30^o from the vertical. The acceleration of the book is A) 5.0 m/s². B) 2.5 m/s². C) 1.0 m/s². D) 9.8 m/s². E) 0 m/s².

Question

Quizplus · Accepted Answer

The force can be resolved into its components parallel and perpendicular to the surface of the floor. The perpendicular component does not contribute to the acceleration, as it is balanced by the normal force of the floor on the book. The parallel component, which is $10\sin(30^\circ) = 5\,\mathrm{N}$, contributes to the acceleration. Using $F=ma$ with $F=5\,\mathrm{N}$ and $m=2.0\,\mathrm{kg}$, we get $a = 5/2.0 = 2.5\,\mathrm{m/s^2}$ in the direction of the force.

A 20 Kg-Book Is at Rest on a Frictionless Horizontal Floor