Class 9 General Science Chapter 7 Question Answer

Complete Notes of Class 9 General Science Chapter 7 Question Answer Energy Notes in 9th Class General Science Urdu Medium by Sir Usman Lateef Suib. These computerized notes are very helpful in the preparation of the Energy Notes for students of the Class 9 General Science Chapter 7 Question Answer these are according to the new paper patterns of all Punjab boards.

• Important Multiple Choice Questions (MCQs) and Short Questions of Chapter No.7: Energy in General Science 9th class Urdu Medium.
• Work and Energy
• Different Forms of Energy
• Interconversion of Energy
• Demand of Energy
• Production of Electrical Energy
• Measurement of Energy
• Energy and the Environment
• Degradation of Environment
• Nuclear Fuel Hazards
• Conservation of Energy
• Energy is the essential part of our lives. Energy is used in our daily life in different forms. We do many tasks from dawn till dark. For this, we have to spend energy. When we get tired after working we feel hungry, we take food which provides us energy. We cannot do any thing without light. Light is also a form of energy. We require heat to warm ourselves in winter. Heat is yet another form of energy.
• In summers, we use fans, refrigerators and air-conditioners for cooling. Besides them, we use many other appliances all of them work with electricity. Electricity provides them energy to run. All of motorbikes, heavy vehicles, aeroplanes and ships consume fuel, which provides energy. As our usage for machines increases, our requirement of energy also increases.
• Work and Energy: For the proper definition of energy, we should first learn about work.
• Work: Suppose a person works in an office for the whole day or a worker holds up a wooden box for half an hour. Apparently both of them have performed work, but in the scientific term this would not be considered as work. There is a proper definition of work in Physics. When a force acts on a body and the body is displaced, then the force is said to have done work on the body.
• "Work is the product of force and distance in the direction of force". i.e., Work Force × Distance covered in the direction of force
• The unit of work is joule (J). The ability of a body to do work is known as energy. Energy is defined as: "Energy is the ability to do work". Since the unit for work is joule therefore, the unit for energy is also joule.
• Different Forms of Energy: There are many forms of energy. Some common forms of energy are as follows:
• (i) Kinetic Energy: When a body is moving, it possesses energy. Because a force is acting on it and it also covers some distance. It means that the body has the ability to do work. "Energy possessed by a body due to its motion is known as kinetic energy".
• When a cricket ball is hit with a bat, the ball runs fast. We say that the running ball possesses kinetic energy. But we observe that ball stops after covering some distance, then where did the kinetic energy go? Actually a force acts on the moving ball in opposite direction, which is ground friction. This frictional force causes the ball to stop. Here the friction of air is negligible.
• The ball has to apply the same amount of force opposite to the frictional force to keep its motion. Thus the ball is doing work against friction, which is the product of its force and the distance covered. All of the kinetic energy of the ball is consumed in doing work and the ball eventually stops. This proves that a body can do work due to kinetic energy.
• The kinetic energy of a body depends upon its mass and speed. The more the mass or speed of a body the more is its kinetic energy.