1. The problem statement, all variables and given/known data The distance between the centers of the wheels of a motorcycle is 155 cm. The center of mass of the motorcycle, including the biker, is 88.0 cm above the ground and halfway between the wheels. Assume the mass of each wheel is small compared with the body of the motorcycle. The engine drives the rear wheel only. What horizontal acceleration of the motorcycle will make the front wheel rise off the ground? 2. Relevant equations [tex]\tau=rFsin\phi[/tex] [tex]\sum\tau=I\alpha[/tex] I am having problems visualizing this question. Any way I look at it, I can't seem to figure out how a horizontal force on the back wheel of the motorcycle would cause the front wheel to move vertically. If I look at it as the rotation of a rigid object, the pivot point would have to be the centre of the back wheel. The torque from the gravity at the centre of mass would have to somehow be negated, right? But the only other force acts horizontally, meaning there would be no force in the vertical direction.