Hi there!
We can use the kinematic equation:
[tex]vf^2 = vi^2 + 2ad[/tex]
vf = final velocity (0 m/s)
vi = initial velocity (15 m/s)
a = acceleration due to breaking (? m/s²)
d = displacement (30 m)
We can plug in the given values:
[tex]0^2 = 15^2 + 2(a)(30)\\\\0 = 225 + 60a[/tex]
Solve:
[tex]-60a = 225 \\\\a = \boxed{-3.75 m/s^2}[/tex]
To solve for the time taken, we can use the following:
[tex]t= \frac{v_f-v_i}{a}[/tex]
Plug in the values:
[tex]t = \frac{0-15}{-3.75} = \boxed{4 sec}[/tex]
