Chapters
Chapter 2: Work and Energy
Chapter 3: Current Electricity
Chapter 4: Measurement of Matter
Chapter 5: Acids, Bases and Salts
Chapter 6: Classification of Plants
Chapter 7: Energy Flow in an Ecosystem
Chapter 8: Useful and Harmful Microbes
Chapter 9: Environmental Management
Chapter 10: Information Communication Technology (ICT)
Chapter 11: Reflection of Light
Chapter 12: Study of Sound
Chapter 13: Carbon : An important element
Chapter 14: Substances in Common Use
Chapter 15: Life Processes in Living Organisms
Chapter 16: Heredity and Variation
Chapter 17: Introduction to Biotechnology
Chapter 18: Observing Space : Telescopes

Chapter 2: Work and Energy
Balbharati solutions for Science and Technology 9th Standard Maharashtra State Board Chapter 2 Work and Energy Exercise [Pages 28 - 29]
Write detailed answer?
Explain the difference between potential energy and kinetic energy.
Write detailed answer?
Derive the formula for the kinetic energy of an object of mass m, moving with velocity v.
Write detailed answer?
Prove that the kinetic energy of a freely falling object on reaching the ground is nothing but the transformation of its initial potential energy.
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Determine the amount of work done when an object is displaced at an angle of `30^circ` with respect to the direction of the applied force.
Write detailed answer?
If an object has 0 momentum, does it have kinetic energy? Explain your answer.
Write detailed answer?
Why is the work done on an object moving with uniform circular motion zero?
Choose one or more correct alternatives.
For work to be performed, energy must be ________
(i) transferred from one place to another
(ii) concentrated
(iii) transformed from one type to another
(iv) destroyed
Choose one or more correct alternatives.
Joule is the unit of ________
(i) force
(ii) work
(iii) power
(iv) energy
Choose one or more correct alternatives.
Which of the forces involved in dragging a heavy object on a smooth, horizontal surface, have the same magnitude?
(i) the horizontal applied force
(ii) gravitational force
(iii) reaction force in vertical direction
(iv) force of friction
Choose one or more correct alternatives.
Power is a measure of the _______
(i) the rapidity with which work is done
(ii) amount of energy required to perform the work
(iii) The slowness with which work is performed
(iv) length of time
Choose one or more correct alternatives.
While dragging or lifting an object, negative work is done by ________
(i) the applied force
(ii) gravitational force
(iii) frictional force
(iv) reaction force
Rewrite the following sentence using proper alternative.
The potential energy of your body is least when you are _____________
sitting on a chair
Sitting on the ground
sleeping on the ground
standing on the ground
Rewrite the following sentence using proper alternative.
The total energy of an object falling freely towards the ground ___________
decreases
remains unchanged
increases
increases in the beginning and then decreases
Rewrite the following sentence using proper alternative.
If we increase the velocity of a car moving on a flat surface to four times its original speed, its potential energy ____________
will be twice its original energy
will not change
will be 4 times its original energy
will be 16 times its original energy.
Rewrite the following sentence using proper alternative.
The work done on an object does not depend on _______
displacement
applied force
initial velocity of the object
the angle between force and displacement.
1. Take two aluminium channels of different lengths.
Questions
1. At the moment of releasing the balls, which energy do the balls have?
Solve the following example.
An electric pump has 2 kW power. How much water will the pump lift every minute to a height of 10 m?
Solve the following example.
If a 1200 W electric iron is used daily for 30 minutes, how much total electricity is consumed in the month of April?
Solve the following example.
If the energy of a ball falling from a height of 10 metres is reduced by 40%, how high will it rebound?
Solve the following example.
The velocity of a car increase from 54 km/hr to 72 km/hr. How much is the work done if the mass of the car is 1500 kg?
Solve the following example.
Ravi applied a force of 10 N and moved a book 30 cm in the direction of the force. How much was the work done by Ravi?
Chapter 2: Work and Energy

Balbharati solutions for Science and Technology 9th Standard Maharashtra State Board chapter 2 - Work and Energy
Balbharati solutions for Science and Technology 9th Standard Maharashtra State Board chapter 2 (Work and Energy) include all questions with solution and detail explanation. This will clear students doubts about any question and improve application skills while preparing for board exams. The detailed, step-by-step solutions will help you understand the concepts better and clear your confusions, if any. Shaalaa.com has the Maharashtra State Board Science and Technology 9th Standard Maharashtra State Board solutions in a manner that help students grasp basic concepts better and faster.
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Concepts covered in Science and Technology 9th Standard Maharashtra State Board chapter 2 Work and Energy are Transformation of Energy, Law of Conservation of Energy, Free Fall, Concept of Power, Definition of Work, Types of Mechanical Energy: Kinetic Energy, Types of Mechanical Energy: Potential Energy, Concept of Energy, Introduction of Work, Measurement of Work, Mechanical Energy and Its Different Forms.
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