Q8E - University Physics with Modern Physics

Question

While driving in an exotic foreign land, you see a speed limit sign that reads 180,000 furlongs per fortnight. How many miles per hour is this? (One furlong is 1/8 mile, and a fortnight is 14 days. A furlong originally referred to the length of a plowed furrow.)

Step-by-Step Solution

Answer

Answer

The speed is 67 miles/hour

Step 1: Conversion of furlong and fortnight

Here,

Furlong and fortnight are the units used in olded days to measure the distance and the time travelled by a person respectively.

According to the data one furlong was considered approximately 1/8th miles. 

Similarly 1 fortnight is considered almost equal to two weeks.

Given data:

Speed limit  in furlongs/fortnight = 180,000 furlongs/fortnight

Other necessary conversions given 

$1 furlong=\frac{1}{8}=miles=0.125mile$

$1 fornight=14days$

Step 2: Conversion into mile/ hour

We know that 1 day contains 24 hour. 

Hence 14 days contain = 24 x 14 hours =336 hour.

We need to convert furlong into mile so we need to multiply the value with 0.125 to convert it into hours. Similarly to convert fortnight into hours we need to divide it with 14 days (two week contains) and also by 24 because each day contain 24 hours.

$$\begin{gathered} =\left(180000\frac{furlongs}{fornight}\right)\times \left(\frac{0.125miles}{1 forlong}\right)\times \left(\frac{1 fornight}{14days}\right)\times \left(\frac{1day}{24h}\right) \\ =67mile/hour \end{gathered}$$

It is therefor concluded that the speed limit is 67 miles/hour.