Kinetic Energy | Prep.1 | Unit 2 - Lesson 2 | Science

شرح ساينس الصف الأول الاعدادي لغات - الفصل الدراسي الثاني
شرح ساينس الاول الاعدادي - ترم تاني

لينك تحميل الملزمة
https://drive.google.com/file/d/1FZx5...

لينك تليجرام
https://t.me/mrahmedelbashagroup

In This Part :
When a book is lifted to a shelf
higher than the ground surface, the work done on the book is stored in form of potential energy When the book is dropped
the work stored in the book is released in form of energy that the object acquires a result of its motion, this energy is known as kinetic energy (KE)

❶ Mass of the object (m)
Activity (1): The effect of the mass of the object on its kinetic energy
Used tools
• Two balls of different masses. • An empty bucket. • A ramp.
Steps
• Release the smaller mass ball to roll down the ramp.
• Repeat the previous step with the larger mass ball.
Observation
The effect of the ball on the empty bucket (the distance the bucket moves) increases with increasing the mass of the ball.
Conclusion
Independent variable: Mass of the ball.
Controlled variables: • Height of the ramp (speed of the ball). • The bucket.
Dependent variable: The distance that the bucket moves
(as a result of the kinetic energy of the ball).
Increasing the mass of the moving object leads to an increase in its kinetic energy, and vice versa.
❷ Speed of the object (v)
Activity (2) : The effect of the speed of the object on its kinetic energy
Used tools
• Two ramps. • Empty bucket. • Ball.
Steps
Release a small mass ball to roll down the ramp (1 ), then to roll down the ramp (2).
Observation
The effect of the ball on the empty bucket (the distance the bucket moves) increases with increasing the height of the ramp (speed of the ball).
Conclusion
Independent variable: Height of the ramp (speed of the ball).
Controlled variables: • Mass of the ball. • The bucket.
Dependent variable: The distance that the bucket moves
(as a result of the kinetic energy of the ball).

Increasing the speed of the moving object leads to an increase in its kinetic energy, and vice versa.

 
The kinetic energy , mass of the object and speed can all be determined, as shown below :

What happens when:

 Activity (3) : The relation between potential energy and kinetic energy
Used tools
Pull the pendulum ball from its original position (A) to position (B).
Release the ball to move freely.
Steps
Pull the pendulum ball from its original position (A) to position (B).
Release the ball to move freely.

Conclusion
• The potential energy of an object is at its maximum at its highest point away from its original position, while kinetic energy is at its maximum when passing through its original position.
• The decrease in potential energy is accompanied by an increase in kinetic energy, such that the amount of the decrease in potential energy equals that of the increase in kinetic energy at any moment, and vice versa.

From the above, we find that:
The sum of the potential and the kinetic energies of the same object at any position throughout its motion equals a constant amount known as mechanical energy (ME).

The mechanical energy (ME) of any object is determined by the following mathematical relation:

 Life Applications
1. Generation of electricity from the High Dam :
The High Dam in Aswan is one of the most important engineering projects in Egypt in the last century in using water energy, where the potential energy of the water held behind the dam is converted into kinetic energy when it rushes downwards.
This kinetic energy of the water
drives turbines that generate electricity in a sustainable way.

2. Demolition Ball :
Demolition ball is used in demolishing old buildings as a result of converting the potential energy stored in the heavy ball which is suspended at a height into kinetic energy upon its release.
This energy is transferred to the building upon the ball impact, causing its demolition.

بالتوفيق
مستر احمد الباشا