Question

two forces, $a=75\\ \text{n}$ and $b=40\\ \text{n}$, act in opposite directions on a box, as shown in the diagram. what is the mass of the box if its acceleration is $9\\ \text{m/s}^2$?
the mass of the box is $\boldsymbol{\square}$ kg.

Explanation:

Step1: Calculate net force

Since forces act opposite, subtract them:
$F_{net} = A - B = 75\ \text{N} - 40\ \text{N} = 35\ \text{N}$

Step2: Rearrange Newton's 2nd Law

Newton's 2nd Law is $F_{net}=ma$, solve for mass:
$m = \frac{F_{net}}{a}$

Step3: Substitute values and compute

Plug in $F_{net}=35\ \text{N}$ and $a=9\ \text{m/s}^2$:
$m = \frac{35}{9} \approx 3.89$

Answer:

The mass of the box is $\boldsymbol{\frac{35}{9} \approx 3.89}$ kg.