Recall that 5280 feet is equal to 1 mile and 3600 seconds is equal to 1 hour.
Then 50 mph is equal to 264000 feet per hour (multiply 50 by 5280).
Then you would divide by 3600 to determine the number of feet in a second:
264000/36 = 73.33 feet per second.
There are other ways to solve this as well (using 1.4667 ft per sec is equal to 1 mph).
Therefore 50 mph would be equal to :
1.4667 * 50 or 73.33 feet per sec