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Physics Question 27 – JEE-MAIN 2026

The increase in the pressure required to decrease the volume (ΔV) of water is 6.3×107 N/m2. The percentage decrease in the volume is _______. (Bulk modulus of water = 2.1×109 N/m2)

The bulk modulus quantifies a substance's resistance to compression under pressure. It relates the change in pressure to the fractional change in volume.

Step 1: Identify the Relevant Formula✦ Active

The bulk modulus (B) is defined as the ratio of the change in pressure (ΔP) to the fractional change in volume (ΔVV). The formula is given by:

B=ΔPΔV/V

Since we are looking for the percentage decrease in volume, we consider the magnitude of the fractional change:

|ΔV|V=ΔPB
Step 2: Calculate the Fractional Decrease in Volume○ Expand

Given values are ΔP=6.3×107 N/m2 and B=2.1×109 N/m2. Substitute these into the formula:

|ΔV|V=6.3×107 N/m22.1×109 N/m2

Perform the calculation:

|ΔV|V=6.32.1×1079=3×102=0.03
💡 Teacher's Secret Hint

Ensure units cancel out correctly, leaving a dimensionless fractional change.

Step 3: Convert to Percentage Decrease○ Expand

To express the fractional decrease as a percentage, multiply by 100%:

Percentage decrease=|ΔV|V×100%=0.03×100%=3%

Thus, the percentage decrease in volume is 3%, which corresponds to option 2.

💡 Teacher's Secret Hint

Remember to multiply by 100 to convert a fraction to a percentage.

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