A block of mass 50kg is placed as a horizontal table. A spring balance is attached to it and is pulled by gradually increasing the force. When the body just moves, the reading of the spring balance is `50N`. Find the coefficient of friction.

Explanation

To find the coefficient of friction for the block on the horizontal table, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Given Values:**
- Mass of the block (m) = 50 kg
- Force at which the block starts moving (F) = 50 N

2. **Calculate the Weight of the Block:**
- The weight (W) of the block can be calculated using the formula:
\[ W = m \cdot g \]
- Where \( g \) (acceleration due to gravity) is approximately \( 9.8 \, \text{m/s}^2 \).
- Substituting the values:
\[ W = 50 \, \text{kg} \cdot 9.8 \, \text{m/s}^2 = 490 \, \text{N} \]

3. **Understanding the Forces Involved:**
- When the block is just about to move, the force applied (F) is equal to the maximum static friction (f_max).
- The maximum static friction can be expressed as:
\[ f_{\text{max}} = \mu_s \cdot N \]
- Where \( \mu_s \) is the coefficient of static friction and \( N \) is the normal force. On a horizontal surface, the normal force \( N \) is equal to the weight of the block \( W \).

4. **Setting Up the Equation:**
- Since \( N = W \), we can rewrite the equation for maximum static friction:
\[ f_{\text{max}} = \mu_s \cdot W \]
- Substituting the values we have:
\[ 50 \, \text{N} = \mu_s \cdot 490 \, \text{N} \]

5. **Solving for the Coefficient of Friction:**
- Rearranging the equation to solve for \( \mu_s \):
\[ \mu_s = \frac{50 \, \text{N}}{490 \, \text{N}} \approx 0.102 \]

6. **Final Result:**
- Therefore, the coefficient of friction \( \mu_s \) is approximately \( 0.102 \).

### Summary:
The coefficient of friction between the block and the table is approximately \( 0.102 \).