Answer:
Explanation: d=vt+frac12at2
where d is the distance, v is the final velocity, a is the acceleration, and t is the time.
We can divide the motion of the car into two parts: the first part when it accelerates from rest to 20 m/s in 4 seconds, and the second part when it maintains a constant speed of 20 m/s for 8 seconds.
For the first part, we have:
v=20 m/s
a=fracvt=frac204=5 m/s$^2$
t=4 s
Plugging these values into the formula, we get:
d1=vt+frac12at2=20times4+frac12times5times42=170 m
For the second part, we have:
v=20 m/s
a=0 m/s$^2$
t=8 s
Plugging these values into the formula, we get:
d2=vt+frac12at2=20times8+frac12times0times82=160 m
Therefore, the total distance travelled by the car is:
d=d1+d2=170+160= 330 m