225 feet
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225 feet is a very vague and most importantly, incorrect answer.
If you know for sure you are throwing 55mph off of a mound, then during a long toss session if you throw a Baseball around a 45-50 degree angle you should be able to reach around 150 feet. 225 feet translates into about 73mph thrown at a 45 degree angle. This is also for the fact that the elevation at which you are is close to sea level and if there is little to no wind.
-R
The equivalent of an 80mph pitch from 47ft at 54ft is 54/47*80 = 91.9 mph.
About 120, if I recall correctly, though it could be less.
6.1 mph = 8.95 feet / second.
40 mph = about 58.6 feet per second.
15 mph = 22 feet per second
55 mph = 80.6666 feet per second
350 feet per second = 238.64 mph
1,200 feet per second = 818.2 mph
69 mph is 101.2 feet per second.
Five mph equates to about 7.333 feet per second.
2,200 feet per second is 1,500 mph
At 1000 mph, there are approximately 1467 feet per second.