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05. Figure 1 shows a simplified model of a hydro-electric power station. Water from a reservoir isdirected to drive a turbine which is at 12 m below the water level of the reservoir. The turbine rotatesat a uniform angular velocity of 9.0 rad s-1 and drives an electric generator through a system shownin Figure 2.(a) (i) If the driving force on an object is F, its velocity is v and its power is P, the relationship betweenthose quantities is given by the following equation. 𝑃 = 𝐹𝑣Show that this equation is dimensionally correct.(ii) A rotating object has torque τ and angular velocity ω about its axis of rotation. Using the equationin (a) (i) above, obtain that; 𝑃 = 𝜏𝜔(b) (i) The flow rate of water in the uniform pipe is 15 kgs-1. Determine the power input to theturbine if 90% of the change in gravitational potential energy of water is achieved by the turbine.(ii) If the cross-sectional diameter of the uniform pipe is 4.0 cm, find the velocity of water flowing alongthe pipe. Take density of water as 1000 kg m-3 and π=3.(iii) Note that the water is flowing at the velocity calculated in (b)(ii) on to the blades of the turbine. Thevelocity of the water flowing out after it hitting the blade is 2.5 m s-1. What is the rate of change ofmomentum of the water stream?(iv) If the average distance from the turbine axis to the center of the blades is 1.0 m, calculate the torqueit produces about its axis.(v) What is the power output of the blade?(vi) Hence, calculate the efficiency of the turbine in transferring mechanical power.Figure 1

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  1. Figure 1 shows a simplified model of a hydro-electric power station. Water from a reservoir isdirected to drive a turbine which is at 12 m below the water level of the reservoir. The turbine rotatesat a uniform angular velocity of 9.0 rad s-1 and drives an electric generator through a system shownin Figure 2.(a) (i) If the driving force on an object is F, its velocity is v and its power is P, the relationship betweenthose quantities is given by the following equation. 𝑃 = 𝐹𝑣Show that this equation is dimensionally correct.(ii) A rotating object has torque τ and angular velocity ω about its axis of rotation. Using the equationin (a) (i) above, obtain that; 𝑃 = 𝜏𝜔(b) (i) The flow rate of water in the uniform pipe is 15 kgs-1. Determine the power input to theturbine if 90% of the change in gravitational potential energy of water is achieved by the turbine.(ii) If the cross-sectional diameter of the uniform pipe is 4.0 cm, find the velocity of water flowing alongthe pipe. Take density of water as 1000 kg m-3 and π=3.(iii) Note that the water is flowing at the velocity calculated in (b)(ii) on to the blades of the turbine. Thevelocity of the water flowing out after it hitting the blade is 2.5 m s-1. What is the rate of change ofmomentum of the water stream?(iv) If the average distance from the turbine axis to the center of the blades is 1.0 m, calculate the torqueit produces about its axis.(v) What is the power output of the blade?(vi) Hence, calculate the efficiency of the turbine in transferring mechanical power.Figure 1
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