Acceleration Due to Gravity (g) MCQs Quiz | Class 9
This Class IX Science (Code 086) quiz covers Unit III: Motion, Force and Work, focusing specifically on Acceleration Due to Gravity (g). The questions test your understanding of the meaning of ‘g’, its standard value, and how it depends on factors like height and location. Take the quiz, review your score, and click “Download Answer PDF” to save your results.
Understanding Acceleration Due to Gravity (g)
Acceleration due to gravity, denoted by the small letter g, is the acceleration gained by an object solely due to the gravitational force of the Earth. When an object is dropped from a height, its velocity increases at a constant rate, which is approximately 9.8 meters per second squared near the Earth’s surface.
Key Concepts & Properties
- Standard Value: The accepted average value of g on the surface of the Earth is 9.8 m/s2. For calculation convenience, it is sometimes rounded to 10 m/s2.
- SI Unit: Since it is an acceleration, its SI unit is m/s2 (meter per second squared).
- Vector Quantity: It has both magnitude and direction. The direction is always towards the center of the Earth.
- Independence of Mass: As demonstrated by Galileo, the value of g does not depend on the mass of the falling object. In the absence of air resistance, a feather and a hammer would fall at the same rate.
Variation of g
The value of g is not constant everywhere. It changes based on location:
- Shape of Earth: The Earth is not a perfect sphere; it is flattened at the poles and bulges at the equator. The radius is smaller at the poles, making g greater there. The radius is larger at the equator, making g smaller there.
- Altitude (Height): As we go higher above the Earth’s surface, the value of g decreases.
- Depth: As we go deep inside the Earth (e.g., into a mine), the value of g decreases. It becomes zero at the exact center of the Earth.
Difference between g and G
| Property | Acceleration due to Gravity (g) | Universal Gravitational Constant (G) |
|---|---|---|
| Value | Varies by location (avg 9.8 m/s2) | Constant everywhere (6.673 x 10^-11 Nm2/kg2) |
| Unit | m/s2 | Nm2/kg2 |
| Quantity | Vector | Scalar |
Practice Questions
Try solving these to test your understanding further:
- If a planet has twice the mass and twice the radius of Earth, how does its g compare to Earth’s g?
- Why does a sheet of paper fall slower than a crumpled ball of paper in air?
- Calculate the weight of a 10 kg object on Earth.
- What happens to the acceleration due to gravity if the Earth suddenly shrinks to half its size but mass remains same?
- Is the value of g positive or negative when throwing a ball upwards?
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