Many of you are familiar with the children’s movie happy feet, about a whimsical penguin chick that just can’t stop dancing. Why don’t these birds fly instead of dance, you ask? Let’s use physics to figure out why Mumble is aerially challenged:
There are four main forces involved in avian air travel: lift, weight, drag, and thrust.
As shown by the diagram of a blue jay in flight (credit to http://www.lcse.umn.edu), lift opposes weight and thrust opposes drag. A bird is able to fly when lift is greater that weight and thrust is greater than drag. Read below for more on these forces:
1. Weight: Mass x acceleration due to gravity
2. Lift: This force can be explained using Bernoulli’s principle—as a fluid’s velocity increases, the pressure decreases and vise versa. Bird wings are in an airfoil shape with a bump on the top and a smooth bottom (like an air plane wing). The air is forced to move faster over the top of the wing than on the bottom because it has a longer distance to travel over the bump. Like faster moving fluids, faster moving air causes the pressure on top of the wing to be lower than on the bottom of the wing, allowing the bird to lift upward.
3. Drag: This force is caused by air resistance. The more aerodynamic the flier, the less drag that will act upon the flier.
4. Thrust: This is the force created to push the bird forward. Birds create thrust by the backward push of their wing, like humans do when we push backward with our arms to swim in a pool. Plane propellers and jet engines create thrust for a plane.
In short, the reason why Mumble cannot fly is because penguins store fat to keep themselves warm, increasing their weight. Their wings also are not the correct shape or size to produce enough lift to get into the air. Weight > Lift, therefore Mumble dances.
Next time, lay off the fish.