Step-by-step explanation:
N/B: Please see attached a rough sketch of the free body diagram for your reference.
From the diagram, the weight W is acting downward and the resultant R is in the positive direction
Given data
mass m=20kg
Forces
Jacob is pulling with 50 N,
Matthew with 40 N, and
Savannah is pulling with 60 N in a negative direction
Required
The net force
Net force= 50+40-(60)
=90-60
=30N in the possitive direction(in Jacob and Mathew's direction)
we know that F=ma
a=F/m
a= 30/20
a=1.5m/s^2
if Mathew decides to run for his life and stop pulling the net force will be
Net force=50-60=-10N (in Savannah's direction)
a=F/m
a=10/20
a=0.5m/s^2