物体受到在一条直线上大小分别为3N和F1的两个力的作用，物体所受合力的大小为13N，则F1的大小可能是______．
本题分两种情况分析：
（1）当这两个力的方向相同时，合力的大小等于二力之和，即3N+F1=13N，解得F1=10N；
（2）当这两个力的方向相反时，合力的大小等于二力之差，即F1-3N=13N，解得F1=16N；
故答案为：10N或16N．
| Choose the correct answers to the questions. 为下列问句选择正确的答语。 |
| ( ) 1. Why don't you jump in the pool? ( ) 2. What does the cloud look like? ( ) 3. What do you wear to swim? ( ) 4. What will you do for the summer holiday? ( ) 5. What is on the tree? | A. It looks like a rabbit. B. It is a bird. C. Because I can't swim. D. I wear a swimsuit. E. I will visit my grandparents. |