College Physics Problem 1.2.8

The speed of sound is measured to be  342 m/s on a certain day. What is this in km/h?


We know that 1 km=1000 m and 1 hr=3600 sec.

Convert 342 m/s.

\displaystyle 342\:m/s=\left(342\:\frac{m}{s}\right)\left(\frac{1\:km}{1000\:m}\right)\left(\frac{3600\:s}{1\:hr}\right)=1231.2\:km/hr          ☚

Therefore, the speed of sound in km/hr is 1231.2 km/hr.

College Physics Problem 1.2.2

A car is traveling at a speed of 33 m/s .
(a) What is its speed in kilometers per hour?
(b) Is it exceeding the 90 km/h speed limit?


Part a

\displaystyle 33\:m/s=\left(33\:\frac{m}{s}\right)\left(\frac{1\:km}{1000\:m}\right)\left(\frac{3600\:s}{1\:hr}\right)=118.8\:km/hr

Part b

At 118.8 km/h, the car is traveling faster than the speed limit.