Pressure MCQs Quiz | Class 9
Class IX Science (Code 086), Unit III: Motion, Force and Work. This quiz covers the definition of pressure, the formula P = Thrust/Area, and various real-life applications. Test your understanding, submit your answers to see your score, and download the PDF solution sheet for revision.
Understanding Pressure in Physics
Pressure is a fundamental concept in Class 9 Science under Unit III (Motion, Force and Work). It helps explain why sharp knives cut better than blunt ones and why heavy vehicles have wide tires.
1. Definition and Formula
Pressure is defined as the force acting perpendicularly on a unit area of a surface. The perpendicular force is also known as Thrust.
- Formula: Pressure (P) = Thrust (F) / Area (A)
- SI Unit: The SI unit of pressure is the Pascal (Pa), named after Blaise Pascal.
- Equivalence: 1 Pa = 1 Newton per square meter (1 N/m2).
2. Factors Affecting Pressure
From the formula P = F/A, we can deduce two main relationships:
- Directly Proportional to Thrust: If the force (thrust) increases while the area remains constant, the pressure increases.
- Inversely Proportional to Area: If the area of contact increases, the pressure decreases. Conversely, if the area decreases, the pressure increases.
3. Applications in Daily Life
| Application | Principle Used | Outcome |
|---|---|---|
| School Bags | Wide straps increase surface area. | Pressure on shoulders is reduced. |
| Knives & Needles | Sharp edges have very small surface area. | High pressure allows easy cutting/piercing. |
| Tractors/Tanks | Broad tires or caterpillar tracks. | Reduces pressure to prevent sinking in mud. |
| Building Foundations | Foundations are made wider than walls. | Reduces pressure on the ground to support weight. |
Quick Revision Points
- Thrust is a vector quantity, but Pressure is a scalar quantity.
- At the same depth, liquid pressure is the same in all directions.
- Atmospheric pressure decreases as we go higher in altitude.
Extra Practice Questions
- Why do camel’s feet not sink into sand?
- Calculate the pressure if a force of 100N acts on an area of 2 m2.
- Why are railway tracks laid on large sized wooden or concrete sleepers?
- Define 1 Pascal.
- How does pressure change if the area is doubled keeping force constant?
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