2. What is Imperative sentence
A type of sentence that gives advice or instructions or that expresses a request or command. 
An imperative sentence typically begins with the base form of a verb, as in Go now!
The implied subject you is said to be "understood"  (You) go now! (See You Understood.)
An imperative sentence ends with a period or an exclamation point

3. When do we use Imperative?
We can use the imperative to give a direct order.
Take that chewing gum out of your mouth.
Stand up straight.
Give me the details.
We can use the imperative to give instructions.
Open your book.
Take two tablets every evening.
Take a left and then a right.
We can use the imperative to make an invitation.
Come in and sit down. Make yourself at home.
Please start without me. I'll be there shortly.
Have a piece of this cake. It's delicious.

4. When do we use Imperative?
We can use the imperative on signs and notices.
Push.
Do not use.
Insert one dollar.
We can use the imperative to give friendly informal advice.
Speak to him. Tell him how you feel.
Have a quiet word with her about it.
Don't go. Stay at home and rest up. Get some sleep and recover.
We can make the imperative 'more polite' by adding 'do'.
Do be quiet.
Do come.
Do sit down.

5. How to form Imperative sentences
Affirmative form            
 Base form of the verb + Object
Open the door.
Let+ me/it/him/her/us/
them+ Base form of the verb
Let me go to Peter's party, please!
Negative form
Do + Not + Base form of the verb + Object
Do not (don't) smoke in public places like hospitals.
them +Not + Base form of the verb
Let's(us) not make noise!
 Note
We can also use: Don't (do not)+Let + me/it/him/her/
us/ them+ Base form of the verb
Don't let him go out tonight!

6. Exercise He should have a job We mustn't stop now. You must go to bed.
You should get up early.
You mustn't stand here.
She can have a drink.
They must clean the carpet.
We needn't wait for him. . 
Ans : Let him have a job
Let us not stop now / Do not let us stop now
Go to bed
Get up early
Do not stand here
Let her have a drink
Let them clean the carpet
Let us not wait for him / Do not let us wait for him

7. Exercise 1. _____ upstairs. (to go)
2. _____ in this lake. ( not/to swim)
3. _____ your homework. (to do)
4. _____ football in the yard. (not/to play)
5. _____ your teeth. (to brush) .  Go
Don’t swim Do
Don’t play
Brush