Work MCQs Quiz | Class 9
This quiz covers Class IX Science (Code 086), Unit III: Motion, Force and Work, specifically focusing on “Work”. The questions address concepts like work done by force, conditions required for work to be done, and the SI unit Joule. Attempt the 10 MCQs below to test your understanding, view your score instantly, and download a detailed PDF answer sheet for revision.
Understanding Work in Physics
In our daily life, we use the term “work” for any mental or physical exertion. However, in physics, Work has a very specific definition. Work is said to be done only when a force applied on an object causes a displacement of the object in the direction of the force.
Scientific Definition of Work
Work is defined as the product of the force acting on an object and the displacement of the object in the direction of the force. It is a scalar quantity, meaning it has magnitude but no direction.
Formula: W = F x s
- W = Work done
- F = Force applied (in Newtons)
- s = Displacement (in meters)
Conditions for Work to be Done
For work to be considered “done” in a scientific sense, two conditions must be satisfied:
- A force should act on an object.
- The object must be displaced.
If the displacement is zero (e.g., pushing a heavy wall that does not move), the work done is zero.
The Unit of Work: Joule
The SI unit of work is the Joule (J). One Joule is defined as the amount of work done when a force of 1 Newton displaces an object by 1 meter along the line of action of the force.
1 Joule = 1 Newton x 1 meter
Types of Work
| Type | Condition | Example |
|---|---|---|
| Positive Work | Force and displacement are in the same direction (angle is 0 degrees). | A horse pulling a cart forward. |
| Negative Work | Force and displacement are in opposite directions (angle is 180 degrees). | Friction acting on a moving car. |
| Zero Work | Displacement is zero OR Force is perpendicular to displacement (angle is 90 degrees). | A porter carrying a load on his head and walking horizontally. |
Key Takeaways for Exam
- Work is the transfer of energy by a force acting on an object as it is displaced.
- Work done against gravity is calculated as W = mgh, where m is mass, g is acceleration due to gravity, and h is height.
- Centripetal force does zero work because the force is always perpendicular to the motion.
Extra Practice Questions
- What is the work done by Earth’s gravity on a satellite moving in a circular orbit? (Answer: Zero)
- If a force of 10 N moves a body by 5 m in the direction of force, calculate work. (Answer: 50 J)
- Is work a vector or scalar quantity? (Answer: Scalar)
- What is the commercial unit of energy related to work? (Answer: Kilowatt-hour)
- Define 1 Joule of work. (Answer: Work done when 1 N force moves object by 1 m)
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