Kids have a tendency to ask for the impossible, whether it be superpowers or a trip to the moon. But when asked by his son to build a rollercoaster in their garden, 'impossible' did not ocur to Californian dad Will Pemble.

The question came after a trip to a nearby theme park, and Will quickly found himself persuaded. He described his reaction to ABC News: “I thought about it for a second and the answer anyone expects is ‘of course not’… but I said 'yes!' I said 'sure!'” 

After six weeks of hard work, the gravity-powered coaster is complete, with its tracks measuring an impressive 60 metres in length. 

But Dad doesn't deserve all the credit. His son Lyle was an equal partner in the project: “He’s a studier. My son knows everything there is to know about rollercoasters. He helps design them and does the math.”

To document their efforts, Will set up CoasterDad.com, a video blog that documented the design and construction of the ride. According to the YouTube description, "The CoasterDad Project is our way of bringing Physics, Family, and Fun to teachers, parents, and kids everywhere."

It may prove to be only the first of many for this father and son team - plans are already underway to work on even bigger coasters.

See the ride in motion below.