问题 计算题

一辆小轿车以15m/s的速度在水平公路匀速行驶,受到的阻力是1200N。小轿车沿水平路面匀速行驶300m驶上一个斜坡。设行驶过程中小轿车的功率始终保持不变。求:

(1)在水平路面行驶时小轿车牵引力所做的功;

(2)行驶过程中小轿车的功率;

(3)要使小轿车上坡时的牵引力增大为水平路面时的1.5倍,其行驶速度应为多少?

答案

(1)3.6×105J (2)1.8×104W  (3)10m/s

题目分析:(1)小轿车在水平路面匀速行驶,牵引力F=F=1200N,牵引力所做的功

W=Fs=1200N×300m=3.6×105J

(2)小轿车在水平路面匀速行驶的时间:

(3)

由于P1=P2所以F1v1=F2v2

.

阅读理解

Once there was a parrot on sale in a pet store. It was a beautiful red and blue bird. It sat on a perch ( 横杆 ) in the middle of the store, so that everyone could see it when they came in. The owner was very proud of it and asked a high price for it.  

One day a man went into the store. “ That’s a beautiful bird,” he said to the owner, “ But why is it so expensive? Is it an unusual bird?”

“ No, it’s not very unusual. It’s expensive because it can talk.” the pet store owner said.

“ I see. How can I make it talk?” the man asked.

The owner asked him, “ Do you see those strings ( 细绳 ) tied to each of the bird’s legs?

“ Yes,” the man answered.

“ Well, you pull those strings,” the pet store owner told him. That will make the parrot talk.”

The man asked, “ Do you mind if I try?”

“ Not at all,” the owner said.

The man walked up to the parrot and pulled the string on its left leg. The parrot said, “ Good morning.”

The man pulled the string on the parrot’s right leg. This time the parrot said, “ How are you today?”

“ That’s not very interesting,” said the man. “ Any parrot could do that.” Then he laughed, “ But what would happen if I pulled both strings at the same time?”

“ I’ll fall off my perch, you fool !”the parrot said.

小题1: The parrot was expensive because ________.

A.it was pretty beautiful

B.it could talk with people

C.it was a very unusual bird

D.it was in the middle of the store小题2:The parrot would talk when ________.

A.people came into the pet store

B.it was the pet store owner

C.people said it was beautiful

D.people pulled the strings on its legs小题3: Which is the first sentence that the parrot said to the man?

A.Good morning.

B.How are you?

C.That wasn’t interesting

D.I’ll fall off my perch, you fool!小题4: From the story we know the parrot was ________.

A.kind

B.silly

C.clever

D.crazy小题5: The best title for the passage should be ________.

Unusual Parrot   B. Parrot Talk      C. Silly Man     D. Clever Owner

填空题