Thrust MCQs Quiz | Class 9
Test your understanding of Class IX Science (Code 086), Unit III: Motion, Force and Work. This quiz covers the meaning of thrust and force acting perpendicular to a surface. Select the best answer for each question, submit to see your score, and download the solution PDF for revision.
Understanding Thrust in Physics
In the context of Class 9 Science, Unit III (Motion, Force and Work), Thrust is defined as the force acting perpendicular to the surface of an object. It is a specific type of force that plays a crucial role in understanding pressure and fluid mechanics.
Key Concepts
- Definition: The total force acting perpendicular (at 90 degrees) to a surface is called thrust.
- Nature: Thrust is a vector quantity because it has both magnitude and direction.
- SI Unit: Since thrust is a force, its SI unit is the Newton (N).
- Relationship with Pressure: Pressure is defined as Thrust per unit Area. Therefore, Thrust = Pressure x Area.
Difference Between Force and Thrust
| Property | Force | Thrust |
|---|---|---|
| Direction | Can act in any direction relative to the surface. | Must act perpendicular (normal) to the surface. |
| Effect | Causes motion or deformation. | Causes pressure on the surface. |
| Unit | Newton (N) | Newton (N) |
Quick Revision Points
- If you stand on loose sand, your feet sink deeper than if you lie down. The thrust is the same in both cases (equal to your weight), but the pressure differs due to the contact area.
- Thrust exerted by a body on a horizontal surface is equal to the weight of the body (mg).
- In fluids, thrust is the force exerted by the fluid perpendicular to the walls of the container or on an immersed object.
Extra Practice Questions
- Q1: A box of mass 10 kg is placed on a table. What is the thrust exerted on the table? (Take g = 10 m/s^2)
Ans: 100 N - Q2: How does thrust change if the area of contact is doubled while keeping the force constant?
Ans: Thrust remains unchanged (Pressure halves). - Q3: Is thrust a scalar or vector quantity?
Ans: Vector. - Q4: What is the CGS unit of thrust?
Ans: Dyne. - Q5: Can thrust act at an angle of 45 degrees to the surface?
Ans: No, by definition, thrust acts at 90 degrees.
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