Question

Estimate the force on a 145-gram baseball if it hits the bat at 50 miles per hour and stays in contact with the bat for 0.1 second, during which time it reverses direction and leaves the bat at 75 miles per hour. Express the result in newtons and in pounds.

Answer 1

 Metric 
====== 
60 miles / hour = 60 * [1 hour / 3600 sec] * [1.6 km/1 mile]*[1000 m / 1 km] 
60 miles / hour = 26.67 m/s 

By similar methods 75 mph = 33.33 m/s 

145 grams = 145 / 1000 = 0.145 kg Why 1000 

F = m*(v1 - v2)/ t I'll let you figure out why v2 is minus. Think about which way the ball is going. 

F = 0.145 kg (26.67 - (- 33.33) ) / 0.1 second 
F = 87 N 

English 
====== 
m = 0.145 kg * 2.2 = 0.319 pounds (mass) 
60 mph = 88 feet per second. 
75 mph = 75 * 5280 / 3600 = 110 feet / second 
F = 0.319 * (88 - - 110)/0.1 
F = 631 poundals.