题目

International Day of HappinessYou might think the International Day of Happiness is a day to practice positive (积极的) thinking or to give thanks for the things in your life that make you happy. But in fact, it’s a United Nations (UN) project which has a more serious purpose. The UN thinks happiness will only be for everyone when the people of the world are equal (平等的).The idea goes back to 1972, when the King of Bhutan, Jigme Singye Wangchuck, said that we should measure (测量) a country’s progress (进步) by its happiness and not just how much it produces or how much money i传送带在工农业生产和日常生活中都有广泛的应用，例如在港口用传送带中运输货物，在机场上用传送带将地面上的行李传送到飞机上等。现有一个水平传送带装置AB，如图所示。传送带的长度L=1m，质量M=1kg的木块随传送带一起以v1=2m/s的速度向左匀速运动(传送带移动的速率始终恒定)，木块与传送带间动摩擦因数μ=0.5。当木块运动到传送带最左端A点时，一颗质量为m=20g的子弹以v0=300m/s水平向右迎面射向木块并从木块中穿出，穿出时速度为u=50m/s。设子弹穿出木块的时间极短，且穿出木块以后子弹未与传送带作用。（传送带装置由电动机带动，传送带与轮子间无相对滑动，不计轮轴处的摩擦，g=10m/s2）(1)试论述木块能否从传送带右端B点离开传送带； (2)在子弹击中木块到木块离开传送带的整个过程中，子弹、木块和传送带这一系统间所产生的总内能是多少；(3)子弹击中木块后，传送带由于传送木块多消耗的电能。