WTMA Center of Gravity and Stability 4 — Questions and Answers
Question 1: A pickup truck's cargo bed has heavy equipment stacked on the left side only. When making a right turn at speed, the truck is most at risk of:
- Sliding forward
- Tipping to the left (driver's side) (Correct answer)
- Tipping to the right
- Skidding straight
Correct answer: Tipping to the left (driver's side)
The off-center load shifts the center of gravity left; centrifugal force during a right turn adds lateral force, increasing tip risk toward the loaded left side.
Question 2: A mechanic is adjusting a machine part and notices it always rolls to the same side when released on a flat surface. This tells her that the part's center of gravity is:
- Exactly at its geometric center
- Offset to the side it rolls toward (Correct answer)
- At the top of the part
- Evenly distributed throughout
Correct answer: Offset to the side it rolls toward
Objects roll toward their center of gravity; if a part consistently rolls to one side, the center of gravity is offset in that direction.
Question 3: Two people carry a heavy door on a horizontal surface. Person A is at one end, Person B at the other. If the door's center of gravity is closer to Person A, then Person A supports:
- Less weight because they are closer to the center
- More weight because the center of gravity is nearer to them (Correct answer)
- Exactly half the weight regardless of center of gravity position
- More weight only if they are taller
Correct answer: More weight because the center of gravity is nearer to them
The carrier closest to the center of gravity bears more of the load because the lever arm to their side is shorter.
Question 4: A construction worker places sandbags at the base of a portable sign to prevent it from tipping over. The sandbags improve stability by:
- Raising the center of gravity of the sign system
- Lowering the center of gravity and widening the effective base (Correct answer)
- Reducing wind resistance on the sign
- Eliminating the sign's torque entirely
Correct answer: Lowering the center of gravity and widening the effective base
Sandbags add low mass that lowers the combined center of gravity and increases resistance to tipping by anchoring the base.
Question 5: An airplane loads cargo into the rear of the fuselage, moving the plane's center of gravity toward the tail. This makes the plane:
- More maneuverable and easier to control
- Tail-heavy, requiring corrective control inputs to maintain level flight (Correct answer)
- More fuel efficient due to reduced drag
- Nose-heavy, requiring more thrust
Correct answer: Tail-heavy, requiring corrective control inputs to maintain level flight
A rearward center of gravity makes an aircraft tail-heavy and less stable longitudinally, requiring constant forward elevator correction.
Question 6: A four-legged stool is more stable than a three-legged stool on a flat floor mainly because:
- Four legs distribute weight more evenly
- Four legs create a larger support polygon than three legs (Correct answer)
- Three legs are always shorter than four
- Four legs reduce the height of the stool
Correct answer: Four legs create a larger support polygon than three legs
The support base of a four-legged stool forms a rectangle, enclosing a larger area than the triangle of three legs, allowing the center of gravity to shift more before tipping.
Question 7: A shelf loaded with books is attached to a wall with two screws — one at the top of the bracket and one at the bottom. Which screw experiences tension (pulling force) when the shelf is loaded?
- The bottom screw
- The top screw (Correct answer)
- Both screws equally
- Neither; only compression acts on the screws
Correct answer: The top screw
The load creates a clockwise torque that tries to pivot the bracket at the bottom screw, pulling the top screw outward from the wall in tension.
WTMA Center of Gravity and Stability 4
A pickup truck's cargo bed has heavy equipment stacked on the left side only.
When making a right turn at speed, the truck is most at risk of: