page number 138 and 139.

Air resistance is a type of friction, but instead of two solid things rubbing together, it’s the air pushing against something that’s moving through it.

Why does it happen?

Air might look invisible, but it’s made of tiny particles (like oxygen and nitrogen molecules). When an object moves through the air—like a car, a bike, a plane, or even a person running—it bumps into those air particles. Those particles push back against the object. That push-back is air resistance.

What affects air resistance?

There are a few things that can make air resistance stronger or weaker:

1. Speed – The faster something goes, the more air particles it hits, and the more resistance it feels.

   Example: A fast car feels more air resistance than a slow one.

   
   

2. Size and shape – Bigger and wider things push more air, so they feel more resistance.

   Smooth or pointed shapes (like race cars or planes) cut through air better, so they feel less resistance.

    Example: A flat piece of paper falls slowly because of lots of air resistance. But if you crumple the paper into a ball, it falls faster because it has less air resistance.

   
   

3. Surface – Smoother surfaces let air slide past easier. Rough surfaces slow things down more.

Real-life examples:

• Parachutes work by creating lots of air resistance, which slows someone down as they fall.

• Bikes and cars are designed to be aerodynamic (smooth and shaped like a teardrop) so they face less air resistance and can go faster.

• Skydivers spread out their arms and legs to increase air resistance and slow their fall.

So in simple terms:

Air resistance is the air trying to slow things down when they move through it. The faster or bigger you go, the more the air pushes back!