Serena Williams Shatters Glass Window with Tennis Ball on David Letterman

Serena Williams has returned to New York to defend her U.S. Open title starting Monday, but she made a quick stop on the Late Show with David Letterman to hit some tennis balls. 

Letterman rallied a bit with Serena, but the real fun started when the tennis star showed off her power. Williams' serve has been clocked at a top speed of 128.6 mph, so it's no wonder Letterman wanted to see if she could break a glass window with a tennis ball. 

Not only did she shatter the glass, she did so wearing high heels and a pencil skirt—and it looked like she wasn't even trying. 

[Late Show with David Letterman, h/t For the Win