Mean effective pressure

When you ride your bike, you push down on the pedals and the bike moves forward. This is similar to how a car's engine works to make the car move. The force that the engine creates is measured as pressure, like how pushing down on the pedals with a lot of force is more pressure than just lightly pushing down.

Now, in a car's engine, there are tiny explosions that happen when fuel is burned. These explosions create a lot of pressure which pushes a piston up and down, making the car's wheels turn. The force of the explosions is spread out over the area that the piston moves in and that's what mean effective pressure is.

Think of it like this - imagine you have a big cardboard box with a lot of candy in it. You want to push the box forward, so you start pushing on it with a lot of force. But if the box is really big, you won't go very far because the force is spread out over a big area. If the box is small, you will go farther because the force is concentrated on a small area.

In a car's engine, the mean effective pressure is like the force you apply to the box. The area that the force is spread out over is the area that the piston moves in. The bigger the area, the less mean effective pressure you'll have, and the smaller the area, the more mean effective pressure you'll have.

So basically, mean effective pressure is a measure of how much force is being applied to the engine piston during the explosions that make the car run, and it takes into account the size of the area that the piston moves in.