The Impulse-Momentum Theorem is represented by the equation ==> (F•t) = (Δp).
From the equation, F and t have an inverse relationship. So if t increases, then F decreases, or vice versa. If we can figure out by what factor t increases then it will be equal to the factor by which F decreases.
So, dividing the larger time period by the smaller time period will give us the factor by which time increases: (0.020s/0.005s) = 4.
Since the time period increases by a factor of 4, then the force F will decrease by a factor of 4. The helmet decreases the size of the collision force by a factor of 4.
