Final answer:
The up-and-down tire movement due to static imbalance is caused by an unevenly balanced tire. This can lead to vibrations or bouncing while driving. Tire balancing is necessary to fix this issue.
Step-by-step explanation:
The up-and-down tire movement due to static imbalance is a phenomenon observed when a car's tires are not evenly balanced. When the tires are not balanced, they can create a static imbalance, causing the car to vibrate or oscillate up and down while driving. This is often felt as a shaking or bouncing sensation.
For example, if one tire is heavier than the others, it will create an imbalance in the rotating mass of the tire. As the heavier portion of the tire rotates, it causes an uneven force on the suspension system, leading to the up-and-down tire movement.
To fix this issue, tire balancing is necessary. Tire balancing involves adding small weights to the rim of the tire to offset any imbalances, ensuring smooth and even rotation.