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**Am I approach this question right?......finding acceleration**

**1. Homework Statement**

A tractor applies a force of 1.3kN to the sled, which has a mass of 1.1x10^4 kg. At that point, the co-efficient of kinetic friction between the sled and the ground has increased to .8. What is the acceleration of the sled?

**2. Homework Equations**

**3. The Attempt at a Solution**

Given

Given

M = 11,000kg

Applied Force = 1300 N , let if be Fa

Kinetic Friction co-efficient = 0.8 , let it be uK

Legend

Legend

let Fa = applied force

let Ff = force of friction

m = mass

a = acceleration

Finding force of friction

Finding force of friction

Ff = uk*Fn

= (0.8)* (11000 kg x 9.81m/s^2)

= 86 328 N

Calculating Acceleration

Calculating Acceleration

F=ma

Fa + Ff = ma

a = ( Fa + Ff ) / m

= ( 1300 N + 86 328 N) / 11 000 kg

= 7.9 m/s^2

I tried to do this question literally 10 times now. I keep getting this answer, but know it's wrong. Maybe my approach isn't correct, or I am missing a negative sign somewhere. Please help.