Question

Using the approximate conversion factors in Table 1.5, convert the following to SI units without using your calculator
a. 20 ft
b. 60 mi
c. 60 mph
d. 8 in

Short answer

a. 20 ft = 6.6 m
b. 60 mi = 96,000 m
c. 60 mph = 30 m/s
d. 8 in = 0.2 m

Step-by-step solution

Write the basic definition of SI units

The system of units used for the measurements of any physical quantity in science is called le Système Internationale d’Unités which iscommonly referred to asSI units.
They are also known as metric units

To convert the given units into SI units

a. 20 ft
SI unit of distance is meter (m).
It is known that
3 feet = 1 meter (approximately)
$$\begin{gathered} \Rightarrow 1feet=0.33meter \\ 20feet=20\times (0.33m) \\ =6.6meters \end{gathered}$$

Thus, 20 ft is equal to 6.6 meters

b. 60 mi
SI unit of distance is meter (m).
It is known that
0.6 mile= 1 km (approximately)

$$\begin{gathered} \Rightarrow 1mile=1.6km \\ 60mile=60\times (1.6km) \\ =96km=96000m \end{gathered}$$

Thus, 60 mi is equal to 96,000 meters

c. 60 mph
SI unit of the time is second (s) and distance is meter (m).
60 mph means 60 miles per hour
It is known that
2mph = 1 m/s (approximately)
$$\begin{gathered} \Rightarrow 1mph=0.5m/s \\ 60mph=60\times (0.5m/s) \\ =30m/sec \end{gathered}$$

Thus, 60 mph is equal to 30 m/sec

d. 8 in
SI unit of distance is meter (m).
It is known that
4 in = 10 cm
$$\begin{gathered} \Rightarrow 1inch=2.5cm \\ 8inch=8\times (2.5cm) \\ =20cm=0.2m \end{gathered}$$
Thus, the 8 in is equal to 0.2 meters