Chapter 10: Work and Energy Application Questions | science Class 9 CBSE

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Chapter 10: Work and Energy Application Questions | science Class 9 CBSE | ByteNotes.in

Application Question

Concept in a practical situation

Application

Question 1

Applied Concept

Q1. Define work and give its SI unit. When is work said to be positive or negative?

Work is force × displacement in the direction of force.
SI unit is joule (J).
Positive work: force and displacement same direction.
Negative work: opposite directions.
Zero work: no displacement or perpendicular force.

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Application Question

Concept in a practical situation

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Question 2

Applied Concept

Q2. State and derive the expression for kinetic energy.

K.E. is energy of motion: K.E. = ½ mv².
Derived using work-energy theorem.
Work done = change in kinetic energy.
As object accelerates, work done increases K.E.
Measured in joules (J).

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Application Question

Concept in a practical situation

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Question 3

Applied Concept

Q3. What is power? Define its SI and commercial units.

Power = Work done / Time.
SI unit: watt (W); 1 W = 1 J/s.
Commercial unit: kilowatt-hour (kWh).
1 kWh = 3.6 × 10⁶ J.
Used for electricity bills.

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Application Question

Concept in a practical situation

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Question 4

Applied Concept

Q4. Define potential energy. Give one example.

Energy stored due to position or configuration.
PE = mgh (mass × gravity × height).
Example: Water stored in a dam.
Higher height = more PE.
Converted into K.E. in turbines.

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Application Question

Concept in a practical situation

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Question 5

Applied Concept

Q5. Define mechanical energy. State its two forms.

Total energy of an object due to motion and position.
Two forms: Kinetic energy (motion) and Potential energy (position).
M.E. = K.E. + P.E.
Conserved in absence of friction.
Examples: Pendulum, projectile motion.

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Question 6

Applied Concept

Q6. Explain conservation of energy with an example.

Energy can neither be created nor destroyed.
It only transforms from one form to another.
Example: Falling object → PE to KE.
Total energy remains constant (ignoring loss).
Applies in all physical systems.

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Chapter sections

Chapter 10: Work and Energy | Application Questions

Q1. Define work and give its SI unit. When is work said to be positive or negative?

Q2. State and derive the expression for kinetic energy.

Q3. What is power? Define its SI and commercial units.

Q4. Define potential energy. Give one example.

Q5. Define mechanical energy. State its two forms.

Q6. Explain conservation of energy with an example.

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