Tóm tắt:

$l_0$=20cm      $m_{Fkéo}$=300g=0,3kg=3N

l=25cm        g=10m/s2

a)$F_{đh}$=k$\left|l-l_0\right|$

<=>3=k.25-20=>k=0,92N/m

b)$F_{đh}$=k$\left|l-l_0\right|$

<=>F=0,92.30-20=7,6N=0,76kg=760kg

45km/h=$\frac{25}{2}$m/s;54km/h=15m/s;72=20m/s

a)a=$\frac{15-{\displaystyle \frac{25}{2}}}{30}$=$\frac{1}{12}$m/s

b)a=$\frac{v-v0}{t}$

<=>$\frac{1}{12}$=$\frac{20-{\displaystyle \frac{25}{2}}}{t}$=>t=90s

6.D

3.D

7.B

5.B

4.B

1.D

2.A

1. Last week, we spent enjoyable picnic in the countryside

2.we get there by bus

3.we are play some game about go fishing and visit paddy fields

4. we are all feel happy and healthy for the trip

gravitation

after picking up trash, make sure you recycle it

1.Although Huong Pagoda Festival is so crowded. We want to go there to pray for happiness.

2. During Tet, Vietnamese people buy all kinds of sweets and make Chung cakes as well.

3.Lan missed the most important part of the festival because she arrived late

1.are

2.get

3.brushe

4.take

5.ha

6.get

7.take

8.get

9.play

10.play

11.helps

22.appearance

23.injury

24.generosity

25.enjoyable

27.inconvenient

28.proud

29.natural

30.products

I have both respect ........and...... admiration for them

He invited Daisy if she would like to drink with him

The teacher told the students to gave him their homework

The man told me not to smoked in the car

The doctor advise me to gave up smoke

She accused Tom that he had told the lie

Mary apologized to Jack for couldn't going to his birthday party the followinng Saturday evening

He promised to finished the work by the end of that week