问题
选择题
在空中匀速水平飞行的飞机，在投放救灾物资的过程中
A．飞机的重力势能不变，动能减小
B．飞机的重力势能减小，动能不变
C．飞机的重力势能减小，动能减小
D．飞机的重力势能增加，动能减小
答案
答案：C
在空中匀速水平飞行的飞机，在投放救灾物资的过程中高度不变，质量减小，所以重力势能减小；速度不变，质量减小，所以动能减小。故选C。
搜题请搜索小程序“爱下问搜题”
在空中匀速水平飞行的飞机，在投放救灾物资的过程中
A．飞机的重力势能不变，动能减小
B．飞机的重力势能减小，动能不变
C．飞机的重力势能减小，动能减小
D．飞机的重力势能增加，动能减小
答案：C
在空中匀速水平飞行的飞机，在投放救灾物资的过程中高度不变，质量减小，所以重力势能减小；速度不变，质量减小，所以动能减小。故选C。
(15) people from around the world came to the eastern Spanish town of Bunol. They threw tons of tomatoes (16) each other in a yearly food fight. That made the street in red juice. A rocket (17) from the town hall was the start of the event for which local government offered 120 tons of tomatoes. Many people, including many from Britain, France, Germany, Russia and Asia, wore hard hats, glasses or protective plastic sheets. (18) protect their things from the sea of red mush (糊状物), shopkeepers (19) huge plastic covers on the front of their stores. About 40,000 people took part in the tomato fight this year, (20) four times the people of the town. (21) amazing! After the fight lasting about one hour, municipal(市政的) workers and local people used big water pipes to clean the streets which were covered with tomato mush. The joiners went to a nearby river to wash (22) . The tomato fight is held each year on the last Wednesday in August. The start of the event is still not clear although it is (23) to have its roots in a food fight between childhood friends (24) in Bunol.
|