# FBISE 9th Class Physics Chapter 6 Work And Energy Short Questions Answers

FBISE 9th class Physics Chapter 6 Work And Energy Short Questions with answers are combined for all 9th class(Matric/ssc) Level students. Here You can prepare all Physics Chapter 6 Work And Energy short question in unique way and also attempt quiz related to this chapter. Just Click on Short Question and below Answer automatically shown. After each question you can give like/dislike to tell other students how its useful for each.

Class/Subject: 9th Class Physics

Chapter Name: Work And Energy

Board: Federal  Board

• Federal Boards 9th Class Physics Annual Examination
• Schools 9th Class Physics December Test
• Federal 9th Class Physics Test
• Entry Test questions related Physics

## FBISE 9th Class Physics Chapter 6 Work And Energy Short Questions Answers

Define Work. What is its SI unit?

Work is done when a force is acting on a
body displaces in the direction of a force. Work is a scalar quantity. It depends on the force acting on a body, displacement of the body, and the angle between them. Its SI unit is Joule (J).

Define Energy?

A body possesses energy if it is capable to do work is known as energy.

Define Watt?

The power of a body is one watt if it does work at the rate of joule per second (1Js-1).

What is meant by the efficiency of a system?

The ratio of the useful work done by a device or machine to the total energy taken up by it is called its efficiency.

Define kinetic energy and give only one example.

The energy possessed by a body due to its motion is called kinetic energy. e.g. Moving water in a river can carry wooden logs through large distances and can also be used to drive turbines for generating electricity.

Define Potential Energy and give examples.

The energy possessed by a body due to its position is known as its potential energy. e.g. stored water in the dam, A hammer is raised to some height can do work.

Define Gravitational potential energy and give example.

The energy present in a body due to its height is called gravitational potential energy. e.g. Stored water in the dam.

What do you know about the Ideal machine?

An ideal machine is that which gives an output equal to the total energy used by it. In other words, its efficiency is 100%. People have tried to design a working system that would be 100% efficient. But practically such a system does not exist.

Define Power. Write down its unit?

The rate of doing work concerning time is called power. Its unit is the watt (W).

When does a force do work? Explain.

Work is said to be done when a force acts on a body and moves it in the direction of the force. Greater is the force acting on a body and longer is the distance moved by it, larger would be the work done. Mathematically, work is a product of force F and displacement S in the direction of the force. Thus
Work done = Force x displacement
Or
W = FS

Why do we need energy?

Energy is an important fundamental concept in science. It links almost all the natural phenomena. When we say that a body has energy, we mean that it can do work, so it possesses energy. The energy of running water can we used the water mills or water turbines.

Why fossil fuels are called non-renewable forms of energy?

Fossil fuels are known as non-renewable resources because it took millions of years for them to attain the present form.

Which form of energy is most preferred and why?

Solar energy is the most preferred. Solar energy is the energy coming from the sun and is used directly and indirectly. Sunlight does not pollute the environment in any way. The sunrays are the ultimate source of life on Earth. We are dependent on the sun for all our food and fuels. If we find a suitable method to use a fraction of the solar energy reaching the Earth, then it would be enough to fulfill our energy requirement.

Name five devices that convert electrical energy into mechanical energy.

i. An electric motor converts electrical energy to mechanical energy
ii. Drill machine
iii. Electric fan
iv. Electric spinner
v. Electric grinder

Name a device that converts mechanical energy into electrical energy.

An electric generator converts mechanical energy into electrical energy.

How can you find the efficiency of a system?

(i) Efficiency = required form of output / total input energy
(ii) % Efiiciency = required for of out put / total input energy x 100

Write down the derivation of potential energy?

Let a body of mass m be raised through height h from the ground. The body will acquire potential energy equal to the work done in lifting it to height h. Thus,
Potential Energy P.E. = F x h
= w x h
(Here weight of the body = w = mg)
P.E. = wh = mgh …………. (i)
Thus, the potential energy possessed by the body for the ground is mgh and is equal to the work done in lifting it to height h.

How is the energy converted from one form to another? Explain.

Energy cannot be destroyed however it can be converted into some other forms.
Rub your hands together quickly. You will feel them warm. You have used your muscular energy in rubbing hands as a result heat is produced. In the process of rubbing hands, mechanical energy is converted into heat energy.

What is a pole vaulter?

A pole vaulter uses a flexible vaulting pole made of special material. It is capable to store all the vaulter’s kinetic energy while bending to the form of potential energy. The vaulter runs as fast as possible to gain speed. The kinetic energy gained by the vaulter due to speed helps him/her to rise as the vaulter straightens. Thus he attains height as the pole returns the potential energy stored by the vaulter in the pole.

Deine mechanical energy with examples.

The energy possessed by a body both due to its motion or position is called mechanical energy. e.g. water running down a stream, a moving car, a lifted hammer, a stretched bow, a catapult, or a compressed spring, etc. Possesses mechanical energy.

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