Acceleration (with and without friction)

[tascja]

Homework Statement

Consider the skier on the slope. She and her equipment have a mass of 60kg. She is on an incline that makes a 25deg incline [she is sliding down the hill].
a. what is her acceleration if friction is negligible?
b. what is her acceleration if friction is known to be 45N?

Homework Equations

Fnet = ma

The Attempt at a Solution

a.
Fnet = ma
588sin25 = 60a
a = 1.30 m/s^2

b.
Fnet = ma
588sin25 - 45 = 60a
a = 2.05 m/s^2

im not sure what I am doing wrong. but the answer book says i should be getting a) 4.41m/s^2 and for b)3.4 m/s^2. If someone could please explain where I am going wrong that would be greatly appreciated :)

 

[jqnsmart]

You seem to be setting up the problem correctly, but the calculation is off. Try instead to find the answer with acceleration isolated (a=F/m). That might make calculating things simpler.