"Mechanical Energy and Its Transformation" Work and Mechanical Energy PPT Courseware 5

Description

"Mechanical Energy and Its Transformation" Work and Mechanical Energy PPT Courseware 5

learning target

1. Understand the mutual conversion of kinetic energy and potential energy. Understand the conversion process of kinetic energy and potential energy through observation and experiment. Can explain some simple physical phenomena related to the mutual conversion of kinetic energy, gravitational potential energy, and elastic potential energy.

2. Know what mechanical energy and the conditions for conservation of mechanical energy are.

1. What is kinetic energy? What does its size relate to?

2. What is gravitational potential energy? What does its size relate to?

3. What is elastic potential energy? What does its size relate to?

The energy an object possesses due to motion is called kinetic energy. Its size is related to quality and speed.

The energy an object has due to being lifted high is called gravitational potential energy. Its size is related to its mass and height of being lifted.

The energy an object possesses due to elastic deformation is called gravitational potential energy. Its size is related to the elastic material and degree of deformation.

1. Mechanical energy:

Kinetic energy and potential energy are collectively called mechanical energy.

1. (The sum of the potential energy and kinetic energy of an object is the total mechanical energy of the object)

2. Kinetic energy is the energy an object has when it moves.

3. Potential energy is stored energy.

2. Conversion of mechanical energy

Demo roll experiment:

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

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

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

Conclusion 2:

Conditions for the mutual conversion of kinetic energy and potential energy

(1) In the process of mutual conversion of kinetic energy and potential energy, there must be changes in kinetic energy and potential energy respectively, and one must increase and the other decrease.

(2) The increase or decrease in kinetic energy should be judged by the increase or decrease in speed.

(3) The increase or decrease in gravitational potential energy should be judged by the increase or decrease in the height of the object from the ground.

(4) The increase or decrease of elastic potential energy should be judged based on the change in deformation size.

3. Conversion and conservation of mechanical energy:

The potential energy and kinetic energy of an object can be converted into each other. If there is no resistance such as friction, then during the mutual conversion of potential energy and kinetic energy, the total mechanical energy remains unchanged, and mechanical energy is conserved.

summary:

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

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

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

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

1. After a skydiver jumps from an airplane in the sky, during the fall before the parachute opens, the athlete’s ( )

A. Kinetic energy increases and gravitational potential energy decreases

B. Kinetic energy decreases and gravitational potential energy increases

C. Kinetic energy decreases and gravitational potential energy decreases

D. Kinetic energy increases and gravitational potential energy increases

2. When an object is acted upon by a pair of balancing forces, its ( )

A. Kinetic energy remains unchanged

B. Kinetic energy may increase or decrease

C. Gravitational potential energy must decrease

D. Gravitational potential energy must increase

3. As shown in the figure, the ball successively starts from rest and slides from the top to the bottom from the smooth inclined plane with the inclination angles of 30° and 60° respectively. The speed when it slides to the bottom is v1 and v2 respectively. Then the following relationship is: the correct one is( )

A. v1>v2 B. v1=v2

C. v1＜v2 D. Unable to determine

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Update Time: 2024-10-18

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

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