The motion is divided into three parts:

1. Acceleration Phase: Initial velocity $u = 0$, Acceleration $a_1 = 2 \text{ m/s}^2$, Time $t_1 = 10 \text{ s}$. Distance $S_1 = ut + \frac{1}{2}at^2 = 0 + \frac{1}{2}(2)(10)^2 = 100 \text{ m}$ .

• Final velocity reached $v = u + at = 0 + 2(10) = 20 \text{ m/s}$.

2. Constant Speed Phase: Velocity $v = 20 \text{ m/s}$, Time $t_2 = 30 \text{ s}$. Distance $S_2 = \text{velocity} \times \text{time} = 20 \times 30 = 600 \text{ m}$.

3. Deceleration Phase: Initial velocity $u' = 20 \text{ m/s}$, Final velocity $v' = 0$, Acceleration $a_2 = -4 \text{ m/s}^2$. Using $v^2 - u^2 = 2aS$: $0^2 - (20)^2 = 2(-4)S_3$.

• $-400 = -8S_3 \implies S_3 = 50 \text{ m}$ .

Total Distance: $S_{total} = S_1 + S_2 + S_3 = 100 + 600 + 50 = 750 \text{ m}$.