An object with a mass of 5 kg5kg is on a surface with a kinetic friction coefficient of 4 4. How much force is necessary to accelerate the object horizontally at 9 m/s^29ms2?

1 Answer
Mar 29, 2016

F_x=5(9-.4*10) ~~25NFx=5(9.410)25N

Explanation:

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Draw a free body diagram, FBD:
x-axis:
sumF_x=ma; F_x-F_(mu_k) = ma Fx=ma;FxFμk=ma Newton Law ===>(1)
Summation of all Forces => mama

y-axis:
sumF_y=ma; F_w-N = 0; F_w=mg=N Fy=ma;FwN=0;Fw=mg=N Newton Law
F_(mu_k)=mu_k *N= mu_k *mgFμk=μkN=μkmg ===>(2)

Insert (2) into (1):

F_x - mu_k *mg = maFxμkmg=ma Solve for F_xFx
F_x = ma-mu_k *mg = m(a-mu_kg)Fx=maμkmg=m(aμkg)

Now m=5kg; mu_k = .4; a=9m/s^2m=5kg;μk=.4;a=9ms2
F_x=5(9-.4*10) ~~25NFx=5(9.410)25N

A word of caution, a kinetic friction, mu_k = 4μk=4 is very large, I suspect you meant to say .4.4 which reasonable. I assumed .4. If you want mu_k = 4μk=4 just correct for it.