# I dont understand this, can you help?

i have a test on friday and i know these kinds of questions will be on it, but i just cant figure it out. here's a real easy version of those questions and i was hoping you guys could clear up for me the basic way to do this:

a man finds that a 6N force will pull a toy wagon along a level table at a constant velocity. He also finds that a 42N force will accelerate the same wagon at 3.0m/s2 along the same table. what is the mass of the wagon?

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ok, do you have the correct answer for this? i'm assuming there's friction or air resistance or something since when you apply the first force there's no acceleration. So you do SumF= ma and i assume there's some counter force (F) that accounts for the zero acceleration. So, 6N + F= m(0), the mystery counter force, (friction or whatever,) is -6. So, i do SumF= ma again with the second force and our new found counter force, and plug in the given acceleration and solve for mass.

I am not a teacher and I am not experienced at explaining or solving mathematics problems.
I reply to hebdens post in order to test my understanding.

Basically your problem is to solve is F= m*a

The force was given, and
The acceleration was given.

Rearranging the formula may help.

Forget the first force value of 6N it is irrelevent at first.

I believe friction can be ignore in this question.

below is starting point. good luck to those who are trying to solve this 4 years later.

F=42N
a=3.0m/s^2
m=?