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

A student pulls on a box up an incline of 10 degrees. The student pulls with a force of 180 N directed at 30 degrees above the line of the incline. The box has a mass of 28 kg, and the coefficient of friction between the box and floor is 0.299. The acceleration of gravity is 9.8 m/s^2.

What is the acceleration of the box?

2. Relevant equations

Fnet = ma

3. The attempt at a solution

From Fnet = ma I get:

Fp - Ffr = ma, where Fp is the force of the person pulling and Ffr is the force of friction resisting.

Ffr = MkFn

Ffr = (.299)(Fn)

I then solved for Fn:

Fn = mg/cos10

Fn = (28)(9.8) / cos10

Fn = 278.63

So Ffr = (.299)(278.63)

Ffr = 83.31 N

So we have Fp - Ffr = ma,

so Fp - 83.31 = (28)a

We need Fp.

Fp = cos30 * 180

Fp = 155.88

So Fp - 83.31 = (28)a,

so 155.88 - 83.31 = (28)a

Solving for a i get a = 2.59 m/s^2

I submitted this to my online homework system and it said the answer was wrong. Where did I go wrong?

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

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

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: Physics Ramp Problem

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