Question: In the Niagara Falls hydroelectric generating plant, the energy of falling water is converted into electricity. The height of the falls is about 50m. Assuming that the energy conversion is highly efficient, approximately how much energy is obtained from one kilogram of falling water? Therefore, approximately how many kilograms of water must go through the generators every second to produce a megawatt of power 1 X 106W?

Short Answer

Expert verified

Answer

The mass of the water is and Energy obtained from 1 kg is 490 Js-1 .

Step by step solution

01

Definition of Energy

The phrase "energy" refers to a person's ability to perform tasks. The potential energy can be defined as kinetic energy, thermal energy, electrical energy, chemical energy, nuclear energy, and other types of energy. There's also the issue of heat and work (energy transmitted from one body to another).

02

Given Information

  • The mass of the water is m = 1 kg .
  • The height of the water from falling is h = 50 m
03

Finding the Potential energy

The energy owned or obtained by an object as a result of a change in its position while in a gravitational field is known as gravitational potential energy.

The energy obtained from 1 kW of falling water by using the formula of the potential energy is where m denotes mass. The g is acceleration due to gravity that is given by , h stands for height.

04

Substitute the values

The formula of work is, where Pis power and tis time.

Substitute and into the formula of work.

W=106×1=106J

Therefore, the work is 106J.

05

 Step 5: Finding the Mass

The potential energy is given by U = mgh.

Substitute, m= 1 kg,g=9.8m/s2and h= 50 m into the formula of potential energy.

U=1×9.8×50=490Js-1

Therefore, the potential energy of 1kg of water is 490 S-1.

Divide the work by the potential energy to find the mass of the water.

Therefore, the mass of the water is and energy created from 1 kg is 490 S-1 .

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Most popular questions from this chapter

Write an equation for the total energy of a system consisting of a mass suspended vertically from a spring, and include the Earth in the system. Place the origin for gravitational energy at the equilibrium position of the mass and show that the changes in energy of a vertical spring-mass system are the same as the changes in energy of a horizontal spring-mass system.

A coffee filter of mass 1.4g dropped from a height of 2m reaches the ground with a speed of 0.8m/s . How much kinetic energyKairdid the air molecules gain from the falling coffee filter?

State which of the following are open systems with respect to energy, and which are closed: a car, a person, an insulated picnic chest, the Universe, the Earth. Explain why.

A coffee filter of mass 1.8kgdropped from a height of 4mreaches the ground with a speed of 0.8m/s. How much kinetic energyKairdid the air molecules gain from the falling coffee filter? Start from the Energy principle, and choose as the system the coffee filter, the Earth and the air.

(a) Using the equation for the amplitudeA , show that if the viscous friction is small, the amplitude is large when ωDis approximately equal toωF . Using the equation involving the phase shiftφ , show that the phase shiftis approximately0° for very low driving frequencyωD , approximately180° for very high driving frequencyωD , and90° at resonance, consistent with your experiment.

(b) Show that with small viscous friction, the amplitudeA drops to12 of the peak amplitude when the driving angular frequency differs from resonance by this amount:

|ωF-ωD|c2mωF

(Hint: Note that near resonanceωDωF , SoωF+ωD2ωF .) Given these results, how does the width of the resonance peak depend on the amount of friction? What would the resonance curve look like if there were very little friction?

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