Answer:
a) 2.2 m/s² b) 8 s
Explanation:
a) Assuming that the acceleration is constant, we can use any of the kinematic equations to solve the question.
As we don´t know the time needed to accelerate, we can use the following equation:
vf2 – vo2 = 2*a*∆x
At first, we can convert the values of vf, vo and ∆x, to SI units, as follows:
vf = 65 mi/h* (1,605 m / 1mi) * (1h/3,600 sec) = 29 m/s
vo = 25 mi/h *(1,605 m / 1mi) * (1h/3,600 sec) = 11.2 m/s
∆x = 0.1 mi*(1,605 m / 1mi) = 160.5 m
Replacing these values in (1), and solving for a, we have:
a = (29 m/s – 11.2 m/s) / 321 m = 2.2 m/s2
b) In order to obtain the time needed to reach to 65 mi/h, we can rearrange the equation for the definition of acceleration, as follows:
vf = vo + at
Replacing by the values already known for vo, vf and a, and solving for t, we get:
t = vf-vo /a = (29 m/s – 11.2 m/s) / 2.2 m/s = 8 sec
