题目

Ellie Carter, 16, is not yet old enough to drive a car in the UK. However, she can fly a plane.Carter became the youngest solo glider pilot (单飞滑翔机飞行员) on her 14th birthday. She completed two six-minute flights near the town of Honiton, UK. On Dec. 1, 2018, she flew solo in a powered plane and became the youngest British person to be licensed (获得正式许可的) to fly a powered plane. Her flight lasted just 10 minutes because of low clouds. But she tries to fly at least once every week. She has spent 75 hours in the sky in total so far.Carter has been interested in flying s2．某同学用如图所示的装置来测定一玩具电动机在稳定状态下的输出功率．实验器材：玩具电动机，带有两个固定铁夹的铁架台，电磁打点计时器，低压交流电源垂锤，细线，米尺，纸带，复写纸片，天平等．实验步骤：（1）如图1所示，将玩具电动机和电磁打点计时器，固定在铁架台上，并与电源接好．把一根细线固定在电动机的转轮上，细线下端连接在重锤上端，将纸带的一端穿过打点计时器的限位孔后，固定在垂锤上．（2）接通打点计时器的电源，启动玩具电动机带动重锤上升．（3）经过一段时间，关闭打点计时器和电动机，取下纸带，进行测量．（4）用天平测出垂锤的质量．已知交流电源周期T=0.02s，当地的重力加速度g=9.80m/s2，某次实验测得垂锤的质量为500.0g，得到纸带的一段如图2所示，试回答下列问题：（1）由纸带上打下的点，可以判断重锤做匀速直线运动．（2）由已知量和测得量求得玩具电动机的输出功率P=2.96W．（保留三位有效数字）