Evel Knievel jumping

[magellan01]

@Sam Stone

Unless a vehicle is balanced right on the center of pressure from air resistence, it will either tilt forward or backwards, depending whether the center of gravity is ahead of or behind the center of pressure.

Hold a hammer parallel to the ground and drop it. The heavy end will drop faster, which means the hammer always falls heavy end down.

Isn’t this a function of wind resistance, not weight? At least that is what Galileo would say. If I misread your post, never mind.

[Philster]

The rear wheel spinning will keep the nose of the bike up. While in the air, the throttle can be used to keep the nose of a motorcycle in the air. Once can see how a powered vehicle such as a cycle has jumping advantages over non-powered vehicles.

If no wheels are present, or not under power…or spinning…there is less opportunity to stay squared away for a good landing.

A motorcycle is one of the better things to jump with. It is narrow, has latent throttle coming of the jump, thenthe throttle can be used to keep the nose up while in flight AND, for added control, applying brakes to the rear wheels will bring the nose down.

[Robot_Arm]

@Pushkin

I thought the idea was that the rear wheels would cause a rotation of the car in the opposite direction, i.e. nose upwards, under acceleration. There was an Evel night on the BBC ages ago, they showed how professional stunt drivers managed their cycles in flight, revving to pull the nose up a little.

I think Sublight was talking about the interval when the front wheels have left the ramp, but the rear wheels are still in contact. Once there’s nothing under the front wheels, they’ll start to fall (a ballistic trajectory, really, but the car will pitch forward compared to its angle on the ramp). If the rear wheels still have traction, and are exerting any force, that force will be in the direction of the ramp and will tend to increase the downward pitch. And the longer the wheelbase of the car, the longer time this effect will take place.

@magellan01

Isn’t this a function of wind resistance, not weight? At least that is what Galileo would say. If I misread your post, never mind.

Those are the forces involved, but unless they act on the exact same point on an object (or in a direct line) they’ll cause an object to rotate as well as move. Gravity acts on the CG (center-of-gravity, the point about which an object would balance), air resistance acts on the center-of-pressure. It’s the same reason darts, or a badminton shuttlecock always orient themselves with one end in front. The same thing would happen with a hammer, or a car, but not as pronounced.

[Cardinal]

As for Brainiac, you realize that Richard Hammond is one of three hosts of Top Gear, but THE host of Brainiac? He’s probably the loudest complainer about caravans on TG, although I’ve decided that the real problem is those 2 lane British roads that don’t let you pass the RV camping people. It basically doesn’t come up in America, except on winding mountain roads, and so you hardly hear about it.