问题 计算题

如图甲所示是某生产流水线的产品输送计数装置示意图.其中S为激光源;R2为保护电阻;R1为光敏电阻,每当产品从传送带上通过S与R1之间时,射向光敏电阻的光线会被产品挡住,R1阻值变大,现让水平传送带匀速前进,输送边长为0.1m、质量为0.6kg的正方体产品,光敏电阻两端的电压随时间变化的图象如图乙所示.

(1)求此产品对传送带的压强(g取10N/kg);

(2)从图中读出每一产品受到激光照射的时间,并求出产品的运动速度;

(3)已知电源电压恒为6V,保护电阻R2的阻值为40Ω,求传送带输送产品过程中光敏电阻1h消耗的电能.

答案

(1)600Pa (2)0.5m/s (3)720J

(1)正方体产品边长0.1m,那么底面积也就是在传送带上的接触面积就是,产品对传送带的压力就等于物体自身重力所以压强

(2)光敏电阻和保护电阻串联,产品通过时,光敏电阻增大,光敏电阻两端电压变大,读乙图,在0.4s到0.6s时间内光敏电阻电压高,说明此时间段是产品通过挡住光照的时间,t=.06s-0.4s=0.2s。已知产品边长为0.1m,所以在0.2s 时间内通过的距离是边长0.1m .那么产品运动的速度

(3)产品通过光敏电阻时,光敏电阻电压为=4v,电源电压为u=6v,那么保护电阻的电压,电流,此时光敏电阻的功率为

没有产品通过光敏电阻时,光敏电阻电压为=2v,电源电压为u=6v,那么保护电阻的电压,电流,此时光敏电阻的功率为

即光敏电阻的电功率一直都是0.2w.

光敏电阻一小时消耗的电能

阅读理解

根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

     As parents, I do not believe that any of us sets out to raise a child that is disrespectful or bratty (无礼的).

Here are some helpful tips on how to raise a bratty child so that you can have a child that will be a benefit to

society.

     It doesn't take long for a toddler (学步儿童) to toddle right into trouble of some kind. This is the perfect

time for parents to teach the child not to do that action again. 1_____ Helping a child to behave in an acceptable

manner is a necessary part of raising the child well. Discipline is a useful teaching tool to guide a child. I think

it's necessary to explain to children what responsibility means. Responsibilities mean the things you have to do.

As parents, you should say to your children "If you play with your toys, it's your responsibility to put them

away." Besides, coach your children in their responsibilities. 2_____ 

     Children should use their time well. We can't let a child do the same thing again and again. When kids are

bored, they can end up in trouble creating problems for themselves and others. 3_____ Children should be told

not to waste their time and they should make full use of their time to do useful things.

     The children who are eager to increase their pocket money should be taught that money does not come

easily. For example, when parents buy school lunch for their children, they should put this spending into

children's pocket money. If children want to get much more money, parents can ask them to cook the lunch

themselves. 4_____ Parents should let their children know how to be in charge of their "expenses" and manage

their expenditure (花费). 

     5_____ It is your responsibility to help and guide your kids. So, the next time you see a bratty kid remember:

they didn't get that way themselves, and they have parents who didn't take time to teach them.

A. Parents should be strict with children.

B. You, the parent, whom kids rely on.

C. This process is called discipline.

D. You should encourage children to be kind.

E. I think it's very important that kids should be coached and not just lectured to.

F. Parents should encourage their children to save their pocket money.

G. Sports, activities and chores are a few things to help give kids something to fill their time.

判断题