A student in your dynamics class has decided to become a stunt bike rider. One of the first stunts undertaken is a long jump on a motorcycle. The student’s inspiration for this was the setting of a world record in jumping 277 feet by professional rider Trigger Gum several years back. Shown below is a split-screen view of the student’s jump. Note that as the rider/bike moves through its jump the rider/bike experiences a clockwise rotation. What causes this rotation (there are no moments on the rider/bike as it moves through space)? Consider an FBD of the rider/bike during the time that the bike wheels are leaving contact with the ramp. Think about the impulse/momentum equation.

As you can see, this rotation creates problems for the landing. Over the course of the long jump, the front of the bike has rotated through a significant clockwise angle. The front wheel lands first, causes the rear wheel to impact the landing ramp, and the bike flips forward.

Watch below how the professional rider, Trigger Gum, took the jump. This bike initially sees the same rotation as for our dynamics student colleague. However, Mr. Gum corrects for this rotation in his jump immediately before landing, allowing the rear wheel to contact first. Do you know what does he does to reverse the bike rotation near landing?

 

Another example of a missed jump
Shown below is a video of a different unsuccessful attempt of a bike onto the roof of a building attempted several years back in Southern California. This rider simply miscalculated the distance from the ramp to the apartment building rooftop. Nobody was hurt on this accident, other than the infliction of embarrassment on the rider.