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.
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