8
xkcd #3244: Pullback Drive
(imgs.xkcd.com)
Title text:
"How does the spring not run out almost immediately?" "We pull it back REALLY far."
Transcript:
Transcript will show once it’s been added to explainxkcd.com
Source: https://xkcd.com/3244/
For this to work, you've gotta bring more weight down than you do back up.
Thankfully, you can just leave all your hopes and dreams at the workplace to make your car lighter on the way back!