Question

Attached here is the question:

Answer 1

t = 6 [s]

Step-by-step explanation:

In order to solve this problem we must first use this equation of kinematics.

`v_(f)^(2)=v_(o)^(2) +2*a*x`

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.

`72 [(km)/(h)]*(1000m)/(1km) *(1h)/(3600s) =20 [m/s]`

`0=(20)^(2) -2*a*60\\400 = 120*a\\a=3.33[m/s^(2) ]`

Now using this other equation of kinematics.

`v_(f)=v_(o)-a*t`

0 = 20-3.33*t

t = 6[s]