Class 9 Science Work, Energy and Simple Machines Solutions | New NCERT Chapter Answers

Work, Energy, and Simple Machines are fundamental concepts in Physics that help us understand how things move and how tasks are accomplished efficiently. From lifting a school bag to riding a bicycle, these concepts play an important role in our daily lives.

The chapter "Work, Energy, and Simple Machines" in the New NCERT Class 9 Science textbook introduces students to the concepts of work, energy, power, machines, and mechanical advantage. Understanding these concepts is essential for building a strong foundation in Physics.

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In this article, you will find complete Class 9 Science Work, Energy and Simple Machines Solutions, important questions, explanations, and exam-oriented answers.

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What is Work?

In Physics, work is said to be done when a force causes displacement in the direction of the force.

The formula for work is:

W = F \times d

Where:

• W = Work done

• F = Force applied

• d = Displacement

SI Unit of Work

The SI unit of work is Joule (J).

Examples of Work

• Pushing a cart forward.

• Lifting a bucket from a well.

• Pulling a suitcase.

Conditions for Work to be Done

Two conditions must be satisfied:

1. A force must act on the object.

2. The object must move in the direction of the force.

If there is no displacement, no work is done.

Example:
Pushing a wall that does not move results in zero work.

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What is Energy?

Energy is the capacity to do work.

Every activity requires energy.

Examples

• Running requires muscular energy.

• A moving car possesses kinetic energy.

• Food provides chemical energy.

Forms of Energy

1. Kinetic Energy

The energy possessed by a moving object is called kinetic energy.

Examples:

• Moving bicycle

• Rolling ball

• Flying bird

Formula:

KE = \frac{1}{2}mv^2

Where:

• m = Mass

• v = Velocity

Complete Class 9 Maths NCERT Solutions | Ganita Manjari Part 1 PDF: Download Now

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2. Potential Energy

The energy possessed by an object due to its position or configuration is called potential energy.

Examples:

• Water stored in a dam

• Stretched rubber band

• Book kept on a shelf

Formula:

Where:

• m = Mass

• g = Acceleration due to gravity

• h = Height

Law of Conservation of Energy

Energy can neither be created nor destroyed. It can only be transformed from one form to another.

Examples:

• Electric bulb: Electrical energy → Light energy

• Fan: Electrical energy → Mechanical energy

• Car engine: Chemical energy → Mechanical energy

What is Power?

Power is the rate at which work is done.

Formula:

P = \frac{W}{t}

Where:

• P = Power

• W = Work done

• t = Time taken

SI Unit of Power

The SI unit of power is Watt (W).

Complete Class 9 Maths NCERT Solutions | Ganita Manjari Part 1 PDF: Download Now

NCERT Solutions for Class 9 Science (New Book) – Chapter-wise PDF: Download Now

Simple Machines

A simple machine is a device that makes work easier by changing the magnitude or direction of force.

Examples

• Lever

• Pulley

• Wheel and Axle

• Inclined Plane

• Screw

• Wedge

Types of Simple Machines

Lever

A lever is a rigid bar that rotates around a fixed point called the fulcrum.

Examples:

• Seesaw

• Crowbar

• Scissors

Parts of a Lever

• Fulcrum

• Effort

• Load

Pulley

A pulley is a wheel with a groove used to lift heavy loads.

Examples:

• Drawing water from a well

• Construction cranes

Wheel and Axle

This machine consists of a wheel attached to a smaller axle.

Examples:

• Bicycle

• Door knob

• Steering wheel

Inclined Plane

An inclined plane is a sloping surface used to move objects with less effort.

Examples:

• Ramp

• Staircase

Mechanical Advantage

Mechanical Advantage tells us how much a machine multiplies the effort applied.

Formula:

MA = \frac{Load}{Effort}

A higher mechanical advantage means less effort is required.

Complete Class 9 Maths NCERT Solutions | Ganita Manjari Part 1 PDF: Download Now

NCERT Solutions for Class 9 Science (New Book) – Chapter-wise PDF: Download Now

Important NCERT Questions and Answers

Q1. What is work?

Answer: Work is done when a force causes displacement in the direction of the force.

Q2. What is energy?

Answer: Energy is the capacity to do work.

Q3. State the SI unit of work.

Answer: Joule (J).

Q4. What is kinetic energy?

Answer: Kinetic energy is the energy possessed by a moving object.

Q5. What is potential energy?

Answer: Potential energy is the energy possessed due to position or configuration.

Q6. What is power?

Answer: Power is the rate of doing work.

Q7. What is a simple machine?

Answer: A simple machine is a device that makes work easier by changing force or direction.

Q8. Define mechanical advantage.

Answer: Mechanical advantage is the ratio of load to effort.

Multiple Choice Questions (MCQs)

1. The SI unit of work is:

A. Newton
B. Joule
C. Watt
D. Pascal

Answer: Joule

2. Energy is the capacity to:

A. Sleep
B. Move
C. Do work
D. Rest

Answer: Do work

3. The SI unit of power is:

A. Joule
B. Newton
C. Watt
D. Meter

Answer: Watt

4. A pulley is used to:

A. Write
B. Lift loads
C. Cut wood
D. Measure force

Answer: Lift loads

5. Mechanical Advantage equals:

A. Effort ÷ Load
B. Load ÷ Effort
C. Work × Time
D. Power × Time

Answer: Load ÷ Effort

Exam Preparation Tips

• Learn all important definitions.

• Practice numerical problems on work, energy, and power.

• Understand different simple machines and their uses.

• Revise formulas regularly.

• Solve NCERT exercise questions and MCQs.

Key Takeaways

• Work is done when force causes displacement.

• Energy is the capacity to do work.

• Kinetic energy is due to motion.

• Potential energy is due to position.

• Power is the rate of doing work.

• Simple machines reduce effort and make work easier.

• Mechanical advantage measures machine efficiency.

Complete Class 9 Maths NCERT Solutions | Ganita Manjari Part 1 PDF: Download Now

NCERT Solutions for Class 9 Science (New Book) – Chapter-wise PDF: Download Now

Conclusion

The chapter Work, Energy, and Simple Machines introduces students to essential Physics concepts used in everyday life. Understanding work, energy transformations, power, and machine efficiency helps students build a strong conceptual foundation for future studies. Regular practice of NCERT questions and numerical problems will help students perform well in examinations and gain confidence in Physics.