A force acting perpendicular to a surface area is called thrust.
Understanding Thrust
Based on the provided reference, the force acting on a body perpendicular to its surface is called thrust. This means when you apply a force that pushes or pulls directly outwards or inwards relative to a surface, without being angled, that specific force is known as thrust.
Think of it as the 'push' or 'pull' that is perfectly straight relative to the surface it's acting upon.
Thrust vs. Pressure
While related, thrust and pressure are distinct concepts. The reference states: Pressure is defined as the thrust acting over a unit area of the surface.
- Thrust is the total force acting perpendicular to a surface. It is a vector quantity, measured in units of force like Newtons (N).
- Pressure is the force per unit area acting perpendicular to a surface. It is a scalar quantity, measured in units of pressure like Pascals (Pa), which are Newtons per square meter (N/m²).
Here's a simple comparison:
| Feature | Thrust | Pressure |
|---|---|---|
| Definition | Force perpendicular to surface | Thrust per unit area |
| Type | Vector (has direction) | Scalar (magnitude only) |
| Units | Newtons (N) | Pascals (Pa or N/m²) |
| Depends on | Total force magnitude & direction | Total force magnitude & area |
Examples of Thrust
Thrust is a concept frequently encountered in physics and engineering:
- Rocket Engines: The force that propels a rocket upwards is the thrust generated by expelling gases downwards. This force acts perpendicular to the base of the rocket relative to its upward motion.
- Fluid Pressure: When a fluid (like water or air) pushes against a submerged or immersed surface, the force it exerts perpendicular to that surface is thrust. The pressure at any point is this thrust distributed over a small area.
- Propellers: Airplane propellers and boat propellers generate thrust by moving air or water, pushing the vehicle forward.
- Standing on the ground: The force your feet exert perpendicular to the ground is a form of thrust. The ground exerts an equal and opposite thrust upwards (the normal force).
In summary, whenever a force is applied directly at a 90-degree angle to a surface, it is specifically termed thrust.
