Question

The speed limit on a highway is 55 mile `h^(-1)`. Express this speed in `SI` base units.
A. `25 ms^(-1)`
B. `35 ms^(-1)`
C. `20 ms^(-1)`
D. `30 ms^(-1)`

Answer 1

Correct Answer - A
Use the relations `1 ft = 12 In`.
`1 "mile" = 5280 ft, 1 "in" = 2.54xx10^(-2) m`, and `1 h = 3600 s`
`"mile" rarr ft rarr "in" rarr m` and `h rarr s`
`(55 ("mile")/(h)) ((580 ft)/(1 "mile")) ((12 "in.")/(1 ft.)) ((2.54xx10^(-2) m)/(1 "in")) ((1h)/(3600 s))`
`= 25 m s^(-1)`