On this place, the truck is steady—there is no such thing as a rotational movement. As earlier than, the gravitational pressure acts on the middle of mass. The pressure from the bottom is not utilized on the middle of mass, however discover that if you happen to prolong a line from that arrow, it could go proper by way of the middle of mass. Which means this pressure additionally has a zero torque arm, so it creates no torque.
However wait. Why does the bottom pressure level that means? It’s really a mixture of two forces: First, there may be the upward-pushing pressure from the bottom. That is an interplay between the tire and the bottom that stops the truck from falling by way of the filth. (It’s the identical pressure that pushes up in your espresso cup to maintain it from passing by way of the desk.) That is referred to as the “regular” pressure, as a result of it’s perpendicular to the floor.
Second, there may be the frictional pressure from the again tires. This pressure pushes ahead, parallel to the bottom. Mix these two and the web pressure factors diagonally as much as the appropriate. That is the entire key to pulling a wheelie: You have to hit the good frictional pressure to purpose that arrow proper on the middle of gravity. That is all driver ability.
You may see that the web pressure causes the truck to speed up ahead. Oh, there’s a solution to do a wheelie with out accelerating. In the event you had the middle of mass immediately over the again wheel, then the pressure from the bottom would push straight up and once more produce zero torque. Nevertheless, on this case I feel the monster truck is accelerating.
The Secret to the Entrance Flip
Now for the finale! So for a truck transferring to the appropriate, you might want to create a clockwise torque to make it somersault ahead. That is fairly robust. The secret’s to have solely the again wheels hit the ramp. And that is precisely what the Mad Scientist driver does, as you’ll be able to see in the video (at 2:00)—as he approaches the ramp, he weapons it right into a wheelie. Here’s a pressure diagram:
Because the entrance wheels are off the bottom, they miss the small ramp—there is no such thing as a pressure exerted on the entrance wheels. Then, when the again wheels hit, the ramp pushes each again and up. The course of this ramp pressure produces the mandatory clockwise torque. This will increase the rotational movement of the truck within the clockwise course. As soon as once more, after it leaves the ramp, it continues to rotate in the identical course so long as it stays aloft. On this case, Mad Scientist completes a full rotation earlier than touchdown. Truthfully, it is fairly spectacular.