CBSE Class 9 Science Extra Questions and Answers for Chapter 11 - Work and Energy are available here for free PDF download. All these questions are based on the NCERT Class 9 Science Book. Students can easily revise all the important concepts by practicing with these questions and increase their chances of scoring good marks in the CBSE Class 9 Science Exam 2020-2021.
CBSE Class 9 Science Extra Questions for Chapter 11 - Work and Energy:
1. When is the work done on an object said to be negative
The work done is said to be negative when force and displacement are in opposite direction.
For example: If a ball is thrown in upwards direction, its displacement would be in upwards direction but the force due to the earth's gravity is in the downward direction.
2. Which two conditions need to be satisfied for work to be done?
Two conditions that need to be satisfied for work to be done are:
(i) a force should act on an object.
(ii) the object must be displaced.
3. Who verified experimentally the law of conservation of energy?
James Prescott Joule
4. How does the work done by an object depends on its motion?
An object moving faster can do more work than an identical object moving relatively slow.
5. What are the two common forms of mechanical energy?
Two common forms of mechanical energy are:
(i) Kinetic energy
(ii) Potential energy
6. Mention the type of energy possessed by the spring of a watch?
Potential energy. This energy is stored as a result of coiling of the string.
7. Write the relation between the commercial unit and the SI unit of energy?
Commercial unit of energy is kilowatt hour (kW h).
SI unit of energy is Joule (J).
Relation between kWh and J is:
∴ 1kWh = 3.6 × 106J
8. Write the expression for energy possessed by an object at a certain height above the ground.
The energy possessed by a body when raised through a height is gravitational potential energy which is expressed as:
Potential energy = mgh
Where, m = mass of object
h = height to which the object is raised
g = gravitational force of earth
9. Is it possible to have work done without the application of force?
No, application of force is a necessary to do work.
10. What kind of energy is possessed by a ball thrown into the air at a point before it reaches its maximum height?
Energy possessed by the ball = Kinetic Energy + Potential Energy = mgh + 1/2mv2
You may download all the above questions and answers in PDF from the link given below:
Students must go through the latest CBSE Syllabus for Class 9 Science so that they can prepare according to the contents prescribed by the board.