# During a test by the editors of an auto magazine, the stopping distanc

During a test by the editors of an auto magazine, the stopping distance s (in metres) of the MacPherson X-2 racing car conformed to the rule
$s=f\left(t\right)=40t-5t2\left(t\ge 0\right)$ where t was the time (in seconds) after the brakes were applied.
a. Find an expression for the cars
You can still ask an expert for help

• Questions are typically answered in as fast as 30 minutes

Solve your problem for the price of one coffee

• Math expert for every subject
• Pay only if we can solve it

a)The velocity is the displacement over time so we divide s by t: $v\left(t\right)=\frac{s}{t}$
$v\left(t\right)=\frac{40t-5{t}^{2}}{t}$
v(t)=40-5t
b)The brakes were first applied at t=0 so using v(t): v(0)=40-5(0)
$v\left(0\right)=40\to 40\frac{m}{s}$
c)Setting v=0, we have 0=40-5t
5t=40
$t=8\to 8$ seconds