一个由静止开始作匀加速运动的物体，它在头4秒内的位移是32米，_爱下问搜题

搜题请搜索小程序“爱下问搜题”

问题填空题

一个由静止开始作匀加速运动的物体，它在头4秒内的位移是32米，则它在第5秒末的速度是______，前2秒内的平均速度是______．

答案

因为物体做初速度为0的匀加速直线运动，根据位移时间关系有：

x=

1

2

at2?a=

2x

t2

=

2×32

42

=4m/s2

则物体在第5s末的速度v₅=at₅=4×5m/s=20m/s

物体在第2s末的速度v₂=at₂=8m/s

所以物体在前2s内的平均速度

.

v

=

v0+v

2

=

0+8

2

m/s=4m/s

故答案为：20m/s，4 m/s

阅读理解

阅读理解。

Come to Jonson’s Store!
Do you like ball games? We have many ball game things. Soccer balls are 20 dollars each. Volleyballs are 25 dollars each. Basketballs are 35 dollars
each. Tennis rackets are 10 dollars each. Ping-pong balls are 1 dollars each.
Ping-pong bats are 10 dollars each.

Come to Huamei Store!
Welcome to Huamei Clothes Store, please! We have jackets at a very
good price---only 35 yuan. For boys, we have socks for 4 yuan each. For
girls, we have skirts for 25 yuan each.

Come and see at Hongxing Store!
Do you need school things? We sell pencil cases for only 2 yuan each. We have great pens for 5 yuan each. A big notebook is 5 yuan and s small one is 3 yuan.

1. Jonson’s Store sells ____________.

A. computer games
B. ball game things
C. clothes
D. school things

2. You can’t buy ___________ at Huamei Store.

A. jackets
B. socks
C. skirts
D. backpacks

3. We can buy a pencil case, a pen and a big notebook for __________yuan.

A. 12
B. 11
C. 9
D. 8

4. At Jonson’s Store, ____________.

A.two soccer balls are 20 dollars
B. a ping

-pong ball is 1 yuan.
C. the volleyball and the basketball have the same price.
D. the tennis racket and the ping-pong bat have the same price.

5. From the three ads, we know____

A. we can buy a volleyball and a basketball for 50 dollars
B. we can buy a sweater for 25 yuan at Huamei Store
C. we can’t buy small notebook at Hongxing Store
D. we can’t buy food at the three stores.

选择题

若集合A={x|-2≤x≤3}，B={x|x<-1或x>4}，则集合A∩B等于 [ ]

A.{x|x≤3或x>4}

B.{x|-1＜x≤3}

C.{x|3≤x＜4}

D.{x|-2≤x＜-1}