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Ten litre of water per second is lifted ...

Ten litre of water per second is lifted from well through 20m and delivered with a velocity of 10 m/s, then the power of the motor is :

A

1.5 kW

B

2.5 kW

C

3.5 kW

D

4.5 kW

Text Solution

AI Generated Solution

The correct Answer is:
To find the power of the motor lifting and delivering water, we need to calculate the work done in two parts: lifting the water from the well and delivering it with a certain velocity. Let's break this down step by step. ### Step 1: Calculate the Work Done in Lifting the Water The work done in lifting the water from the well can be calculated using the formula: \[ \text{Work} = m \cdot g \cdot h \] Where: - \( m \) = mass of water (in kg) - \( g \) = acceleration due to gravity (approximately \( 9.81 \, \text{m/s}^2 \)) - \( h \) = height (in meters) Given: - The volume of water lifted per second = 10 liters = 10 kg (since 1 liter of water has a mass of approximately 1 kg) - Height \( h = 20 \, \text{m} \) Substituting the values: \[ \text{Work}_{\text{lifting}} = 10 \, \text{kg} \cdot 9.81 \, \text{m/s}^2 \cdot 20 \, \text{m} \] \[ \text{Work}_{\text{lifting}} = 1962 \, \text{J} \, (\text{Joules}) \] ### Step 2: Calculate the Work Done in Delivering the Water The work done in delivering the water at a velocity can be calculated using the kinetic energy formula: \[ \text{Work} = \frac{1}{2} m v^2 \] Where: - \( v \) = velocity (in m/s) Given: - Velocity \( v = 10 \, \text{m/s} \) Substituting the values: \[ \text{Work}_{\text{delivery}} = \frac{1}{2} \cdot 10 \, \text{kg} \cdot (10 \, \text{m/s})^2 \] \[ \text{Work}_{\text{delivery}} = \frac{1}{2} \cdot 10 \cdot 100 \] \[ \text{Work}_{\text{delivery}} = 500 \, \text{J} \, (\text{Joules}) \] ### Step 3: Calculate the Total Work Done Now, we can find the total work done by adding the work done in lifting and delivering: \[ \text{Total Work} = \text{Work}_{\text{lifting}} + \text{Work}_{\text{delivery}} \] \[ \text{Total Work} = 1962 \, \text{J} + 500 \, \text{J} \] \[ \text{Total Work} = 2462 \, \text{J} \] ### Step 4: Calculate the Power of the Motor Power is defined as work done per unit time. Since the work is done in one second: \[ \text{Power} = \frac{\text{Total Work}}{\text{Time}} \] \[ \text{Power} = \frac{2462 \, \text{J}}{1 \, \text{s}} \] \[ \text{Power} = 2462 \, \text{W} \] To convert this into kilowatts: \[ \text{Power} = \frac{2462}{1000} = 2.462 \, \text{kW} \] ### Final Answer The power of the motor is approximately **2.46 kW**. ---
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