Answer:
t = 6 [s]
Explanation:
In order to solve this problem we must first use this equation of kinematics.
[tex]v_{f}^{2}=v_{o}^{2} +2*a*x[/tex]
where:
Vf = final velocity = 0 (the car comes to rest)
Vo = initial velocity = 72 [km/h]
a = acceleration [m/s²]
x = distance = 60 [m]
First we must convert the velocity from kilometers per hour to meters per second.
[tex]72 [\frac{km}{h}]*\frac{1000m}{1km} *\frac{1h}{3600s} =20 [m/s][/tex]
[tex]0=(20)^{2} -2*a*60\\400 = 120*a\\a=3.33[m/s^{2} ][/tex]
Now using this other equation of kinematics.
[tex]v_{f}=v_{o}-a*t[/tex]
0 = 20-3.33*t
t = 6[s]
