汽车发动机的额定功率为Pm，它在水平路面上行驶时受到的阻力大小恒定。若汽车在水平路面上由静止开始作直线运动，发动机输出功率P随时间t变化的图象如图所示，则
| A．0~t1时间内汽车做变加速运动，t1~t2时间内汽车做匀加速直线运动 |
| B．0~t1时间内汽车做匀加速运动，t1~t2时间内汽车可能先做加速度逐渐减小的变加速运动，而后再做匀速直线运动 |
| C．0~t1时间内汽车牵引力逐渐增大，t1~t2时间内牵引力保持不变 |
| D．0~t1时间内汽车牵引力恒定，t1~t2时间内牵引力与阻力大小相等 |
相关试题
用所给单词的适当形式填空。
（1）Do you like _____________ (make) kites?
（2）We must ______________ (do) our homework now.
（3）________(not run) on the grass, please.
（4）Sunday is the ________(one) day of the week.
（5）All the teachers are very (exciting).
（6）The sign on the ________(bird) cage is very interesting.
（7）The diary ________ (be) in your bag just now.
（8）He usually ___________(get) up at six o’clock
Where ______ you two days ago? I _____ in Beijing.
| A．Was, were | B．Were, was | C．Was, was | D．Were, were |
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