Question

Suppose a car is traveling at +20.3 m/s, and the driver sees a traffic light turn red. After 0.207 s has elapsed (the reaction time), the driver applies the brakes, and the car decelerates at 7.00 m/s2. What is the stopping distance of the car, as measured from the point where the driver first notices the red light?

Answer 1

Answer:

33.6371 m

Explanation:

t = Time taken

u = Initial velocity = 20.3 m/s

v = Final velocity

s = Displacement

a = Acceleration = -7 m/s²

Distance traveled in the 0.207 seconds

Distance = Speed × Time

⇒Distance = 20.3×0.207 = 4.2021 m

Equation of motion

$v^2-u^2=2as\\\Rightarrow s=\frac{v^2-u^2}{2a}\\\Rightarrow s=\frac{0^2-20.3^2}{2\times -7}\\\Rightarrow s=29.435\ m$

Distance traveled by the car while braking is 29.435 m

Total distance measured from the point where the driver first notices the red light is 29.435+4.2021 = 33.6371 m