(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A 1.0 kg physics book is on a 20 degree slope. It is connected by a string to a 500 g coffee cup dangling at the bottom side of the incline. The book is given a push up the slope and released with a speed of 3.0 m/s. The coefficients of friction are us = .50 and uk = .20.

a. How far does the book slide?

b. At the highest point, does the book stick to the slope, or does it slide back down?

2. Relevant equations

F=m*a

vf^2 = vi^2 + 2as

3. The attempt at a solution

So I found four forces: Tension of the rope pulled by the weight, fk (friction force), force of gravity at a 20 degree angle, and normal force.

n = mgcosx = (9.8)(1)cos20 N.........fk = uk*n = (.2)n = 1.842 N

T = mass of cup * 9.8 = 4.9 N

Fg = mgsinx = (1)(9.8)sin20 = 3.35 N

...so I get (Fnet)x = ma = -4.9N - 1.842N - 3.35N = -10.095

...so... a = (-10.095)/(1) = -10.095 m/s^2

But when I put this value of acceleration into vf^2 = vi^2 + 2as, or 0=9 + 2(-10.095)s, I get .446m.

The correct answer is .67m. What did I do wrong? I'm pretty sure it's around the (Fnet)x part.

Thanks for any help.

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: 1.0kg physics book on slope, and Newton's Third Law?

**Physics Forums | Science Articles, Homework Help, Discussion**