Final answer:
The conversion of 78.9 cm/s to km/hr is not listed among the provided options as it equals 2.8404 km/hr. However, if the intended conversion was to m/s, then it would be 0.789 m/s, which is similar to option A if considering m/s.
Step-by-step explanation:
To convert a speed from centimeters per second (cm/s) to kilometers per hour (km/hr), we need to change the units from centimeters to kilometers and seconds to hours. One kilometer is 100,000 centimeters, and one hour is 3,600 seconds. So, to make this conversion, you multiply the speed in cm/s by the conversion factor of (1 km / 100,000 cm) to change centimeters to kilometers, and then by the conversion factor of (3,600 s / 1 hr) to change seconds to hours.
Applying these conversion factors to 78.9 cm/s:
- 78.9 cm/s × (1 km / 100,000 cm) = 0.000789 km/s,
- then 0.000789 km/s × 3,600 s/hr = 2.8404 km/hr, which is not one of the options provided, indicating a potential mistake in the question.
However, if we assume the correct unit in the given options was cm/s, and the question means to ask which of the listed speeds matches 78.9 cm/s when converted to m/s, we find:
- 78.9 cm/s × (1 m / 100 cm) = 0.789 m/s,
which matches option A after considering m/s instead of km/hr.