Case 1: Take two books and place them on a table on top of each other. Keep the position of the bottom book constant and slides the top book over its surface.
Case 2: Now, place a few pencile in between the two books. Again, move the top book with respect to the bottom book
In which of the two cases did you have to exert lesser force?

Explanation

To determine in which case you have to exert lesser force when sliding the top book over the bottom book, let's analyze both cases step by step.

### Step-by-Step Solution:

**Step 1: Understanding Case 1**
- In Case 1, you have two books placed on top of each other on a table. The bottom book remains stationary while you slide the top book over the surface of the bottom book.
- Here, the force you exert to move the top book has to overcome the sliding friction between the two books.

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