Initial speed of the three-wheeler, $u=36\, km / h$

Final speed of the three-wheeler, $v=10 \,m / s$

Time, $t=4\, s$

Mass of the three-wheeler, $m=400 \,kg$

Mass of the driver, $m^{\prime}=65\, kg$

Total mass of the system, $M=400+65=465 \,kg$

Using the first law of motion, the acceleration ( $a$ ) of the three-wheeler can be calculated as: $v=u+a t$

$\therefore a=\frac{v-u}{t}=\frac{0-10}{4}=-2.5 \,m / s ^{2}$

The negative sign indicates that the velocity of the three-wheeler is decreasing with time.

Using Newton's second law of motion, the net force acting on the three-wheeler can be calculated as:

$F=M a$

riaccademy.nett

$=465 \times(-2.5)=-1162.5\, N$

The negative sign indicates that the force is acting against the direction of motion of the three-wheeler.