Situation: hang a pen by a piece of string question: is the pen at rest or in motion? are there forces actiong on the pen ?
situation:cut the spring with a pair of scisssors
question: what happens to the pen ? what could have caused the pen's motion?
situation: a book on top of a table
question: is the book at rest or in motion ? are there forces acting on the book?



Situation 1: Hanging pen  
1. The pen is at rest. 
2. Yes. The forces acting on the pen are the force exerted by the string on the pen and the force of gravity. 
3. When we cut the string, the pen fell to the ground because gravity pulled on it downward.   
Situation 2: Book on a table  
4. The book is at rest. 
5. Yes. The forces acting on the book are the force exerted by the table on the book and the force of gravity. 

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