Answer:
option (b) 0.71 km
Explanation:
Given:
Initial speed of the car, v = 69 mph = 69 × 0.44704 m/s = 30.84 m/s
final speed of the car, u = half the initial speed = 30.84 m/s / 2 = 15.42 m/s
acceleration, a = -0.5 m/s²
Now,
from the Newton's equation of motion, we have
v² - u² = 2as
where, s is the distance traveled
on substituting the respective values, we have
30.84² - 15.42² = 2 × (-0.5) × s
713.329 = -1 × s
or
s = 713.329 m (since the distance cannot be negative)
or
s = 0.713 km
hence,
the correct answer is option (b) 0.71 km
