# Mary applies a force of 71 N to push a box with an acceleration of 0.54 m/s2. When she increases the pushing force to 80 N, the box's acceleration changes to 0.69 m/s2. (a) What is the mass of the box?

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There is a constant friction force present between the floor and the box.

There is a constant friction force present between the floor and the box.

##### 1 Answer

Mar 13, 2017

I got

#### Explanation:

We can use Newton's second law where the resultant of all forces is equal to mass times acceleration.

Where

From the first equation we have:

Substitute into the second equation: