Which chemical follows the law of conservation of mass

Bernie drove home from a vacation in 1.5 hours. he traveled a total distance of 60 miles. what was his average speed in miles per hour? a. 60 mph b. 90 mph c. 40 mph d. 55mph

Rank the automobiles based on the magnitude of the force needed to stop them, from largest to smallest.2000 kg car going 5m/s500 kg car going 20 m/s1000 kg car going20m/s500 kg car going10m/s1000 kg car going10/s4000 kg car going 5m/s 0 0 603

The frequency of the fundamental of the guitar string is 320 hz. at what speed v do waves move along that string?