University:
Boston University
Course:
CAS PY 252 | Principles of Physics 2
Academic year:

2019
Views:

162

Pages:

13
Author:

Clint W.

11.5 Torque and Center of Gravity If the center of gravity of an object is above the area of support, the object will remain upright. 11.5 Torque and Center of Gravity The block topples when the CG extends beyond its support base. 11.5 Torque and Center of Gravity The Rule for Toppling If the CG extends outside the area of support, an unbalanced torque exists, and the object will topple. 11.5 Torque and Center of Gravity This “Londoner” doubledecker bus is undergoing a tilt test. So much of the weight of the vehicle is in the lower part that the bus can be tilted beyond 28° without toppling. 11.5 Torque and Center of Gravity The Leaning Tower of Pisa does not topple because its CG does not extend beyond its base. A vertical line below the CG falls inside the base, and so the Leaning Tower has stood for centuries. If the tower leaned far enough that the CG extended beyond the base, an unbalanced torque would topple the tower. 11.5 Torque and Center of Gravity The Leaning Tower of Pisa does not topple over because its CG lies above its base. 11.5 Torque and Center of Gravity The support base of an object does not have to be solid. An object will remain upright if the CG is above its base of support. 11.5 Torque and Center of Gravity The shaded area bounded by the bottom of the chair legs defines the support base of the chair. 11.5 Torque and Center of Gravity Balancing Try balancing a broom upright on the palm of your hand. The support base is quite small and relatively far beneath the CG, so it’s difficult to maintain balance for very long. After some practice, you can do it if you learn to make slight movements of your hand to exactly respond to variations in balance. 11.5 Torque and Center of Gravity Gyroscopes and computerassisted motors in the selfbalancing electric scooter make continual adjustments to keep the combined CGs of Mark, Tenny, and the vehicles above the support base. 11.5 Torque and Center of Gravity The Moon’s CG Only one side of the moon continually faces Earth. • Because the side of the moon nearest Earth is gravitationally tugged toward Earth a bit more than farther parts, the moon’s CG is closer to Earth than its center of mass. • While the moon rotates about its center of mass, Earth pulls on its CG. • This produces a torque when the moon’s CG is not on the line between the moon’s and Earth’s centers. • This torque keeps one hemisphere of the moon facing Earth. 11.5 Torque and Center of Gravity The moon is slightly footballshaped due to Earth’s gravitational pull. 11.5 Torque and Center of Gravity What is the rule for toppling?