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

2.40 *10^{2}N force is pulling 85.0 kg refrigerator across a horizontal surface. The force acts at an angle of 20.0 degrees above the surface. The coefficient of kinetic friction is 0.200 and the fridge moves a distance of 8.00 m. Find the the work done by the kinetic frictional force and the pulling force.

2. Relevant equations

Equation 1

W = F(cos(angle))*s

s = displacement

Equation 2

Fs = Fn * coefficient of kinetic friction

3. The attempt at a solution

So I'm just working to get the work done by the kinetic frictional force first. My answer doesn't match the book's though.

Fn - mg + 240sin20= m*ay

Fn - mg + 240sin20 = 0

Fn = mg - 240sin20

Put Fn = mg into equation 2.

Fs = Fn * coefficient of kinetic friction

Fs = (mg - 240sin20) * coefficient of kinetic friction

Put into equation 1

W = F(cos(angle))*s

W = (mg - 240sin20) * coefficient of kinetic friction(cos(angle))*s

Solve

W = (85kg*9.8m/s^{2}- 240sin20) * 0.200(cos(20))*8m

W = 1130 J

Book says -1.2*10^{3}J

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# Homework Help: Work done by constant force

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