）的力作用在同一质点上，它们的合力的大小
满足（ ） 
2/4单选题
难度：
2.
如图所示，用两根绳子吊着一个物体，逐渐增大两绳间的夹角，物体始终保持静止，则两绳对物体的拉力的合力（ ）
如图所示，用两根绳子吊着一个物体，逐渐增大两绳间的夹角，物体始终保持静止，则两绳对物体的拉力的合力（ ） | A | 大小不变 |
| B | 逐渐增大 |
| C | 逐渐减小 |
| D | 先减小后增大 |
正确答案：QQ==
5Yqb55qE5ZCI5oiQ
3/4单选题
难度：
3.三个共点力
，
，
则（ ）
，，则（ ） | A |  可能是 与 的合力 |
| B | 可能是与的合力 |
| C | 可能是与的合力 |
| D | 以上三种说法都不正确 |
- 提示1：
- 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
正确答案：RA==
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
4/4单选题
难度：
4.大小分别为
和
的两个共点力，同时作用在一个物体上，对于合力大小的估计，下列说法正确的是（ ）
和的两个共点力，同时作用在一个物体上，对于合力大小的估计，下列说法正确的是（ ） | A | 一定不能等于 |
| B | 一定不能大于 |
| C | 一定不能小于 |
| D | 一定大于等于且小于等于 |
- 提示1：
- IOW9kzxpbWcgd2lkdGg9MTMgaGVpZ2h0PTE3IHNyYz0iaHR0cHM6Ly9wMi5xaW5nZ3VvLmNvbS9HMS9NMDAvNUIvQjEvckJBQ0ZGT1RNelBqbHVSdkFBQUJKaUxWZ253NDI2LnBuZyI+5Li65Lu75oSP6KeS5pe277yM5qC55o2u5L2Z5bym5a6a5b6L77yM5ZCI5YqbPGltZyB3aWR0aD0xNjUgaGVpZ2h0PTI4IHNyYz0iaHR0cHM6Ly9wMS5xaW5nZ3VvLmNvbS9HMS9NMDAvOTcvQkUvckJBQ0UxT1RNek9oeGN0SUFBQURzQlY2YW9jNjE3LnBuZyI+
- 提示2：
- IOaXoOiuuuS4pOS4quWKm+eahOWkueinkuS4uuWkmuWwke+8jOW/heeEtuaciTxpbWcgd2lkdGg9MTMyIGhlaWdodD0yNCBzcmM9Imh0dHBzOi8vcDIucWluZ2d1by5jb20vRzEvTTAwLzVCL0IxL3JCQUNGRk9UTXpPeWhrWG5BQUFDbVNkV3QzUTM5MC5wbmciPuaIkOeri++8jOWNszxpbWcgd2lkdGg9ODUgaGVpZ2h0PTE5IHNyYz0iaHR0cHM6Ly9wMS5xaW5nZ3VvLmNvbS9HMS9NMDAvNUIvQjEvckJBQ0ZGT1RNelB5NXg5S0FBQUNTQ3puRDdRNzY0LnBuZyI+Lg==
正确答案：Qg==
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