Senna often helps her grandfather in his vehicle recycling company in the Netherlands. If she needs to remove the wheels of a car, she uses a jack. A jack is very handy because it is a lever. With levers you don't need much strength to lift heavy objects. Senna starts to investigate the power of levers and pulleys among the old cars of her grandfather. She builds a secret drawer that can only be opened using a lever, she cracks a walnut with a door and she tries to lift a car using only muscle power and a few pulleys.

Originally released by Nederlandse Publieke Omroep, 2014. Streaming video file encoded with permission for digital streaming by Infobase on August 11, 2016.