# Homework Help: What did I do wrong? (Newton's Second Law)

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1. Oct 19, 2014

### glenohumeral13

1. The problem statement, all variables and given/known data
(This is a problem I made up, so if the problem is with the problem, let me know.)
A 500N ball is being pushed down a carpeted decline of 24° to the horizontal. It starts from 1 m/s and ends the 20 foot (6.1 m) decline at 32 m/s. What is the coefficient and force of kinetic friction and applied force?

2. Relevant equations
I used:
Fg = mag, F = ma, a = μkg, and vi = √(vf2 - (2ad)).

3. The attempt at a solution
Fg = mag
50N = m(9.81)
m = 5kg
1 = √(322 - 2a(6.1))
1 = √(1024 - 12.2a)
1 = √(1011.8a)
1 = 38√(a)
1/38 = √(a)
.022 = a
a = .0004 m/s2
F = ma
F = 5*.0004
F = .002N
a = μkg
.0004 = μk(9.81)
μk = .000040775

2. Oct 20, 2014

### CWatters

Does that value for "a" seem reasonable to you?

I know the equation as...

a = (vf2 - vi2)/2d

a = (1024 - 1) / (2*6.1)
= 84m/s2

3. Oct 20, 2014

### CWatters

PS: It may not be your only error. I haven't checked.

4. Oct 20, 2014

Thanks.