A bar magnet makes 40 oscillations per minute in a vibration magnetometer. An identical magnet is demagnetised completely and is placed over the magnet in the magnetometer. Calculate the time taken for 40 oscillations by this combination. Ignore induced magnetism.

Explanation

To solve the problem step by step, let's break it down:

### Step 1: Understand the given information
- A bar magnet makes 40 oscillations per minute in a vibration magnetometer.
- An identical magnet is completely demagnetized and placed over the first magnet.
- We need to calculate the time taken for 40 oscillations by this combination.

### Step 2: Calculate the time period for the first magnet
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