Question

What's the runners acceleration with a mass of 80 kg?

Answer 1

It depends on the force

If force is f and acceleration is a then the equation would be

a= f/80 kg

Answer 2

The runner's acceleration depends on the net force acting on him.
His acceleration is going to be ...

(net force on him, in Newtons) divided by (80 kg) .

The unit of the acceleration is meters/second-squared .

The direction of the acceleration is the same as the direction
of the net force.