Question

the speed limit on some interstate highways is roughly 135 km/h. (a) what is this in meters per second? (b) how many miles per hour is this?

Explanation:

Step1: Convert km to m and h to s for part (a)

We know that 1 km = 1000 m and 1 h=3600 s.
The conversion factor for km/h to m/s is $\frac{1000\ m}{3600\ s}=\frac{5}{18}\ m/s$ per km/h.
So, $135\ km/h\times\frac{5}{18}\ m/s\ per\ km/h = 37.5\ m/s$.

Step2: Convert km to miles for part (b)

We know that 1 mile = 1.60934 km.
To convert km/h to mi/h, we use the conversion factor $\frac{1\ mi}{1.60934\ km}$.
So, $135\ km/h\times\frac{1\ mi}{1.60934\ km}\approx83.88\ mi/h$.

Answer:

(a) 37.5
(b) 83.88