| ||
| 2g |
小球在水平方向上受到电场力作用而作匀加速直线运动，则
水平位移：x＝
| 2v0 |
| 2 |
又h＝
| v0 |
| 2 |
联立得，x=2h=
| ||
| g |
故M、N间的电势差为UMN=-Ex=-
| U |
| d |
| ||
| g |
U
| ||
| dg |
从M运动到N的过程，由动能定理得
W电+WG=
| 1 |
| 2 |
| 1 |
| 2 |
| v | 20 |
又WG＝−mgh＝−
| 1 |
| 2 |
| v | 20 |
所以联立解得，W电＝2m
| v | 20 |
答：M、N间电势差为-
U
| ||
| dg |
| v | 20 |
| ||
| 2g |
| 2v0 |
| 2 |
| v0 |
| 2 |
| ||
| g |
| U |
| d |
| ||
| g |
U
| ||
| dg |
| 1 |
| 2 |
| 1 |
| 2 |
| v | 20 |
| 1 |
| 2 |
| v | 20 |
| v | 20 |
U
| ||
| dg |
| v | 20 |