"Hmm... very clever. You got the first one right. Now try this on for size: You and a zombie are skating at an ice rink on a date."

You involuntarily gag a bit.

"What, you've got a problem with dating zombies? Hah! I've been dead since 1727, and I still haven't landed a date with one. You should be so lucky! Anyway where was I... ah yes. So you give the zombie a push with constant force for one second, which gets the zombie going pretty fast. Now the zombie comes to a stop. You push the zombie again with twice the force. How long do you have to push the zombie to get it going the same speed?"