Suppose a car is traveling at 18.6 m/s, and the driver sees a traffic light turn red. After 0.500 s has elapsed (the reaction time), the driver applies the brakes, and the car decelerates at 4.00 m/s2. What is the stopping distance of the car, as measured from the point where the driver first notices the red light

s = 52.545 m

Explanation:

First, we calculate the distance covered during the 0.5 s when the driver notices the light and applies the brake.

where,

s₁ = distance covered between noticing light and applying brake = ?

v = speed = 18.6 m/s

t = time = 0.5 s

Therefore,

Now, we calculate the distance for the car to stop after the application of brakes. For that we use 3rd equation of motion:

where,

s₂ = distance covered after applying brake = ?

a = deceleration = - 4 m/s²

Vf = final speed = 0 m/s

Vi = initial speed = 18.6 m/s

Therefore,

So the total distance covered by the car before stopping is:

s = 52.545 m

fgravity=10x10=100n case 1

fgravity=30x20=600n case 2

6 times more

i would say