The # &*%$ Book Is Back Again

st More Newt’s 1 Law (a = 0 ↔ Fnet = 0) Problems

Find the missing forces required by Newt’s 1st Law. Start by sketching the missing vector using our color coding scheme, using green for the force of gravity, red for the normal force between the book and the table, blue for a force of push and orange for a force of friction. Use hash marks to indicate vectors that are the same length. Fill in the box with the numerical value of each missing vector.

1. The book remains at rest on an inclined ramp. Note: the contact force f = is always perpendicular to the surface F = 4 N friction of contact, and the force of friction is N . always parallel to the surface of contact.

Hint: Redraw the vectors by adding F = 5 N them in a right triangle to find the grav force of friction.

2. Three students are fighting over a physics PJ that is resting on a smooth (frictionless) table. Isaak pulls with a force of 55 N due east. Liam pulls with a force of 75 N due south. John says “That book is mine!” and pulls with just the right amount of force to balance the other two, keeping the book at rest. A small victory to be sure, but at least Isaak didn’t get it! Find the force, magnitude and direction, that John applies on the book.

Top View: not to scale!

F = John PHYSIC θ = S F = 55 N Isaak

F = 75 N Liam