题干

一个人稳站在商店的自动扶梯的水平踏板上,随扶梯向上加速运动,如图所示,则

A:人对踏板的压力大小等于人受到的重力大小

B:人只受到重力和踏板的支持力作用

C:人受到的力的合力对人所做的功等于人的重力势能和动能的增加量

D:踏板对人做的功等于人的机械能的增加量

上一题 下一题 0.0难度 选择题 更新时间:2012-03-20 07:59:45

答案(点此获取答案解析)

D

同类题1

任务型阅读

Ways to say “Happy birthday to me”

    Tomorrow is my birthday, and I'm at an age when not everyone looks forward to cakes and presents.____It always makes me feel excited to be alive and grateful for my life and my family. So I think even if your birthday is a regular old day at work or home, there are some easy ways to raise it to the special occasion.

    Give a gift to someone else.____While everyone loves to open a birthday present, there is a lot of joy and goodness to be gained from being generous with others. Making a birthday donation(捐赠)to a charity that means something to you.____.

    Try something new. Today is new to us. Why not enjoy the newness of the moment? Dip your tones into some new waters, sign up for an adult education class, go for a new-to-you park or plan a new trip.____

    ____Whether or not you have the opportunity to share a meal, outing or party with friends and family, please take time on your birthday to connect with people who are important to your life. if you use social media like phones, you are likely filled with well-wishes from loved ones. Use these as a jumping-off point to start new conversations and reconnect with people who lift your spirits and support in your journey towards being your best self.

A. Connect with people who matter to you.

B. Freshen up yourself with countless opportunities.

C. It's better to give than to receive

D. This year my birthday is on a Saturday.

E. I love my birthday, though.

F. Download an app to learn a new language is also a good choice.

G. One choice is to donate a dollar amount to match your age.