The distance of the object from the lens is 3.12 cm.
<h3>What is magnification?</h3>
Magnification is the process of of enlarging an apparent size of an object.
<h3>Object distance</h3>
The object distance is calculated using the following lens formula;

where;
- M is the magnification
- V is the image distance
- U is object distance

Thus, the distance of the object from the lens is 3.12 cm.
Learn more about object distance here: brainly.com/question/24894435
According to Newton's 2nd law of motion, F =ma = 80x5 = 400N.