It is required to increase the velocity of a scooter of mass $80 \ kg$ from $5 \ m s^{-1}$ to $25 \ m s^{-1}$ in $2 \ s$. Calculate the force required.

(D) Given: mass $m = 80 \ kg$,initial velocity $u = 5 \ m s^{-1}$,final velocity $v = 25 \ m s^{-1}$,and time $t = 2 \ s$.
First,calculate the acceleration $a$ using the formula:
$a = \frac{v - u}{t}$
Substituting the values:
$a = \frac{25 - 5}{2} = \frac{20}{2} = 10 \ m s^{-2}$
Now,calculate the force $F$ using Newton's second law of motion:
$F = m \times a$
Substituting the values:
$F = 80 \ kg \times 10 \ m s^{-2} = 800 \ N$
Therefore,the force required is $800 \ N$.