I have this homework question: A sled is pulled with a horizontal force of 15 N along a level trail, and the acceleration is found to be 0.40 m/s2. An extra mass m = 4.3 kg is placed on the sled. If the same force is just barely able to keep the sled moving, what is the coefficient of kinetic friction between the sled and the trail?(adsbygoogle = window.adsbygoogle || []).push({});

Important equations:

Fk = uk *N

F = ma

Attempt to solve:

Sum of all forces = ma

sum of all forces = Fpull - Fk

Fpull - Fk = ma

Fpull - ma = Fk

Fpull - ma = uk *N

(Fpull - ma)/mg = uk

I'm unable to solve since I don't know what the original mass was, since it says 4.3 extra mass was added. Can someone help me out??

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# Homework Help: Find the Coefficient of Kinetic Friction

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