A mason worker throws the bricks ot a height of 10m, at which the bricks reach with a velocity of `6ms^(-1)`. The percentage of energy he is wasting is nearly `(g=10ms^(-2)0`

Options

A. 0.15
B. 0.18
C. 2.2
D. 0.36

Answer

To solve the problem, we need to calculate the potential energy and kinetic energy of the brick when it reaches a height of 10 meters and then determine the percentage of energy wasted by the mason worker.

### Step-by-Step Solution:

1. **Calculate the Potential Energy (PE) at Height:**
The potential energy (PE) of the brick at a height \( h = 10 \, \text{m} \) is given by the formula:
\[ PE = mgh \]
where \( g = 10 \, \text{m/s}^2 \) and \( h = 10 \, \text{m} \).
\[ PE = m \cdot 10 \cdot 10 = 100m \, \text{J} \]

2. **Calculate the Kinetic Energy (KE) at the Height:**
The kinetic energy (KE) of the brick when it reaches the height with a velocity \( v = 6 \, \text{m/s} \) is given by:
\[ KE = \frac{1}{2} mv^2 \]
Substituting \( v = 6 \, \text{m/s} \):
\[ KE = \frac{1}{2} m \cdot (6)^2 = \frac{1}{2} m \cdot 36 = 18m \, \text{J} \]

3. **Calculate Total Energy (TE):**
The total energy (TE) when the brick reaches the height is the sum of potential energy and kinetic energy:
\[ TE = PE + KE = 100m + 18m = 118m \, \text{J} \]

4. **Calculate Wasted Energy:**
The wasted energy is the kinetic energy that the brick has when it reaches the height, which is not converted into potential energy. Thus, the wasted energy is:
\[ \text{Wasted Energy} = KE = 18m \, \text{J} \]

5. **Calculate Percentage of Energy Wasted:**
The percentage of energy wasted can be calculated using the formula:
\[ \text{Percentage Wasted} = \left( \frac{\text{Wasted Energy}}{\text{Total Energy}} \right) \times 100 \]
Substituting the values:
\[ \text{Percentage Wasted} = \left( \frac{18m}{118m} \right) \times 100 = \left( \frac{18}{118} \right) \times 100 \approx 15.25\% \]

### Conclusion:
The percentage of energy wasted by the mason worker is approximately \( 15.25\% \).