题干

质量为m、长度为L的通电技术杆ab水平搁置在两压力传感器上(杆与传感器绝缘).处于磁感应强度为B,垂直纸面向里的匀强磁场中,金属与磁场垂直.如图所示.金属杆中的电流大小和方向均可以改变,但金属杆一直处于静止状态,两压力传感器度数时刻保持一致,重力加速度为g,则:

上一题 下一题 0.0难度 选择题 更新时间:2016-12-09 09:10:19

答案(点此获取答案解析)

同类题3

阅读理解

    Amy Maplethorpe, a first-year speech-language teacher at Raymond Ellis Primary School, used tennis balls, a hot glue gun, Mod Podge and a bit of paint to create two chairs that help students with sensory (感官的) problems.

    According to the school's Facebook page, which became very popular, the chairs provide a “different texture (质地) to improve sensory regulation (调控).”

    Maplethorpe told ABC News that the chairs will service about 15 to 20 students. Children with sensory problems often have a hard time “dealing with sensory information”. Things, such as coats, blankets and Maplethorpe's chairs, often comfort a student.

    Maplethorpe was excited to create the chair after seeing something similar on a website, and she made some changes to the idea.

    “I wanted to continue to help students with sensory problems at Ellis and provide a different kind of seat for the students,” she continued. “I was excited that this chair could help my students.''

    The two chairs are now in the school's sensory room, which was created recently, according to headmaster, Beth Kiewicz.

    “When a child's sensory needs are met, we then can move on to their needs in study,” Kiewicz, who has led the school for six years, told ABC News.

    Maplethorpe said the chairs have already made a difference for some of her students.

    “Students have become more patient, and have followed directions, while waiting for activities,” she said.