The decrease in the potential energy of a ball of mass 20kg which falls from a height of 50 cm is

Options

A. 98 J
B. 968 J
C. 1980 J
D. None of these .

Explanation

To find the decrease in potential energy of a ball of mass 20 kg that falls from a height of 50 cm, we can follow these steps:

### Step-by-Step Solution:

1. **Convert Height to Meters**:
- The height given is 50 cm. We need to convert this to meters since the standard unit of height in physics is meters.
- \( h = \frac{50 \text{ cm}}{100} = 0.5 \text{ m} \)

2. **Identify the Mass**:
- The mass of the ball is given as \( m = 20 \text{ kg} \).

3. **Use the Acceleration Due to Gravity**:
- The acceleration due to gravity \( g \) is approximately \( 9.8 \text{ m/s}^2 \).

4. **Calculate the Decrease in Potential Energy**:
- The formula for potential energy (PE) is:
\[ \Delta PE = m \cdot g \cdot h \]
- Substitute the values into the formula:
\[ \Delta PE = 20 \text{ kg} \cdot 9.8 \text{ m/s}^2 \cdot 0.5 \text{ m} \]

5. **Perform the Calculation**:
- First, calculate \( 20 \cdot 9.8 = 196 \).
- Then, multiply by \( 0.5 \):
\[ 196 \cdot 0.5 = 98 \text{ J} \]

6. **Conclusion**:
- The decrease in potential energy of the ball when it falls from a height of 50 cm is \( 98 \text{ J} \).

### Final Answer:
The decrease in potential energy is **98 Joules**.