"Mechanical Energy and Its Transformation" Work and Mechanical Energy PPT Courseware 2

Description

"Mechanical Energy and Its Transformation" Work and Mechanical Energy PPT Courseware 2

Review questions

1. What is the definition of kinetic energy? Influencing factors?

2. What is the definition of gravitational potential energy? Influencing factors?

3. What is the definition of elastic potential energy? Influencing factors?

learning target

1. Use examples to illustrate that kinetic energy and potential energy can be converted into each other.

2. Be able to explain simple phenomena related to the mutual conversion of kinetic energy, gravitational potential energy, and elastic potential energy.

3. Preliminarily understand the meaning of conservation of mechanical energy.

4. Understand water energy and wind energy

Roll experiment:

A. Ascent: speed ______, kinetic energy ______, height ______, gravitational potential energy ______, _______ energy is converted into ______ energy.

B. Descending: speed ______, kinetic energy ______, height ______, gravitational potential energy ______, _______ energy is converted into ______ energy.

Experiments show:

Kinetic energy and gravitational potential energy can be converted into each other. When resistance is ignored, mechanical energy is conserved.

1. Conservation of mechanical energy

If only kinetic energy and potential energy are converted into each other, although the magnitude of kinetic energy and potential energy will change, the total mechanical energy will not change, or mechanical energy is conserved.

illustrate:

1. The conservation of mechanical energy is conditional. When only gravity or elastic force does work, mechanical energy is conserved.

2. In the mutual conversion of kinetic energy and potential energy, if there is resistance such as friction, the total mechanical energy will be reduced.

3. Words such as "on a smooth surface" and "without air resistance" indicate that there is no resistance such as friction. At this time, the total mechanical energy can be regarded as unchanged.

Have you ever paid attention to physics in life?

Why do you pedal a few times before riding a bicycle uphill?

Answer: Because pedaling a few times will increase the speed and kinetic energy, so that more kinetic energy can be converted into gravitational potential energy to prevent the car from going backwards.

The spring door can close by itself after being pushed open. This is because after the door is pushed open, the spring is tightened and deformed, and has _______ energy. When it is let go, it is converted into the _____ energy of the door, causing the door to close automatically.

4. Utilization of water energy and wind energy

1. Among the following statements about water energy and wind energy, which one is correct ( )

A. The flowing river water only has kinetic energy and no gravitational potential energy.

B. Wind only has kinetic energy, not gravitational potential energy

C. Both water energy and wind energy can be used to do continuous work.

D. Neither water energy nor wind energy will pollute the environment.

2. When building a hydropower station, the purpose of building a barrage is to store the __________ of the water. When the sluice is opened, the __________ of the river water can be converted into _________ that can impact the turbine to generate electricity.

3. Wind energy is relatively easy to use and does not ________. But wind energy ________, ("stable" or "unstable") is also not easy to store.

Consolidation exercises:

1. When a skydiver falls in the air at a constant speed, gravitational potential energy _______, kinetic energy _______, and mechanical energy _______.

2. When Xiao Ming is sliding down the smooth slide, which of the following statements is correct (not counting air resistance) ( )

A. Gravitational potential energy decreases, kinetic energy increases, and mechanical energy remains unchanged.

B. Gravitational potential energy increases, kinetic energy decreases, and mechanical energy remains unchanged.

C. Gravitational potential energy increases, kinetic energy remains unchanged, and mechanical energy increases.

D. Gravitational potential energy decreases, kinetic energy remains unchanged, and mechanical energy decreases.

3． A sprinkler truck driving at a constant speed on a level street sprays water on the road as it travels. Which of the following statements about the change in mechanical energy is correct ( )

A. Kinetic energy remains unchanged, mechanical energy decreases

B． Kinetic energy decreases, mechanical energy decreases

C. Kinetic energy remains unchanged, mechanical energy remains unchanged

D． Kinetic energy decreases and mechanical energy increases

Summary

Kinetic energy and potential energy can be converted into each other

1. Kinetic energy and potential energy are collectively called mechanical energy.

2. Kinetic energy and gravitational potential energy can be converted into each other

Kinetic energy and elastic potential energy can be converted into each other

3. Conservation of mechanical energy: If only kinetic energy and potential energy are converted into each other, the total mechanical energy remains unchanged.

4. Utilization of water energy and wind energy

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Update Time: 2024-10-31

This template belongs to Physics courseware People's Education Edition Physics for Grade 8, Volume 2 industry PPT template

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