问题 填空题

某物体挂在弹簧测力计的下端,弹簧测力计的示数为19.6牛,把它浸没在水中,弹簧测力计的示数是4.9牛,则该物体受到的浮力是______牛,若将该物体浸没在酒精(ρ=0.8/cm3)时,弹簧测力计的示数______4.9牛(填<,>或=).

答案

(1)该物体受到的浮力:

F=G-F′=19.6N-4.9N=14.7N;

(2)物体浸没在酒精中时,排开酒精的体积和排开水的体积相等,

∵FgV,且酒精的密度小于水的密度,

∴物体浸没酒精时,受到的浮力变小,

∵F=G-F′,

∴F′=G-F>4.9N,即弹簧测力计的示数大于4.9N.

故答案为:14.7;>.

填空题
完形填空

Directions: Complete the following passage by using the words in the box. Each word can only be used once. Note that there is one word more than you need.

A. alert    B. classify      C. commit   D. delicately   E. gentle     F. impose

G. labels   H. moderation    I. relieve    J. signals      K. simply

Let's say you've decided you want to eat more healthfully. However, you don't have time to carefully plan menus for meals or read food __小题1:__ at the supermarket. Since you really__小题2:__ yourself to a healthier lifestyle, a little help would come in handy, wouldn't it? This is where a "choice architect" can help__小题3:__some of the burden of doing it all yourself. Choice architects are people who organize the contexts in which customers make decisions. For example, the person who decides the layout of your local supermarket-including which shelf the peanut butter goes on, and how the oranges are piled up—is a choice architect.

Governments don't have to__小题4:__healthier lifestyles through laws  for example, smoking bans. Rather, if given an environment created by a choice architect-one that encourages us to choose what is best-we will do the right things. In other words, there will be designs that gently push customers toward making healthier choices, without removing freedom of choice. This idea combines freedom to choose with__小题5:__hints from choice architects, who aim to help people live longer, healthier, and happier lives.

The British and Swedish governments have introduced a so-called "traffic light system" to __小题6:__foods as healthy or unhealthy. This means that customers can see at a glance how much fat, sugar, and salt each product contains__小题7:__by looking at the lights on the package. A green light __小题8:__that the amounts of the three nutrients are healthy; yellow indicates that the customer should be__小题9:__; and red means that the food is high in at least one of the three nutrients and should be eaten in __小题10:__. The customer is given important health information, but is still free to decide what to choose.