A wooden stick 2m long is floating on the surface of water. The surface tension of water 0.07 N/m. By putting soap solution on one side of the sticks the surface tension is reduced to 0.06 N/m. The net force on the stick will be

Options

A. 0.07 N
B. 0.06 N
C. 0.01 N
D. 0.02 N

Answer

To solve the problem, we need to calculate the net force acting on the wooden stick floating on the surface of water when soap solution is applied on one side. Here are the steps to find the solution:

### Step 1: Understand the Forces Due to Surface Tension
The force due to surface tension acts along the length of the stick. The total force due to surface tension can be calculated using the formula:
\[ F = \text{Surface Tension} \times \text{Length} \]

### Step 2: Calculate the Force on the Side without Soap
The surface tension of water is given as \( 0.07 \, \text{N/m} \) and the length of the stick is \( 2 \, \text{m} \). Therefore, the force due to surface tension on the side without soap is:
\[ F_1 = 0.07 \, \text{N/m} \times 2 \, \text{m} = 0.14 \, \text{N} \]

### Step 3: Calculate the Force on the Side with Soap
After applying soap solution, the surface tension is reduced to \( 0.06 \, \text{N/m} \). The force due to surface tension on the side with soap is:
\[ F_2 = 0.06 \, \text{N/m} \times 2 \, \text{m} = 0.12 \, \text{N} \]

### Step 4: Calculate the Net Force
The net force acting on the stick can be found by subtracting the force on the side with soap from the force on the side without soap:
\[ F_{\text{net}} = F_1 - F_2 = 0.14 \, \text{N} - 0.12 \, \text{N} = 0.02 \, \text{N} \]

### Conclusion
The net force acting on the stick is \( 0.02 \, \text{N} \).