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

33.6371 m

Step-by-step 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=(v^2-u^2)/(2a)\\\Rightarrow s=(0^2-20.3^2)/(2* -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