Water resistance

Experiment with water and differently-shaped objects to feel the force of water resistance. Optionally relate to why some water animals have wide feet.
Science content
Biology: Features, Adaptations of Living Things (K, 1, 3, 7)
Lessons activity is in
  • tray of water
  • stiff plastic e.g. plastic table mats or similar
  • popsicle stick other rod to make a handle
  • stapler
  • images of duck, otter beaver and grebe feet
  • or alternative to above: tall cylinder of water and modelling clay

Use one of two set-ups to feel the force of water resistance.

1. Fill a tray with water.
Cut out shapes from the stiff plastic e.g. different shapes of animal feet.
Drag the shapes through the tray of water to feel the water pushing against them.
Compare how much the shapes can push the water / the water pushes on the different shapes.

2. Fill a cylinder with water.
Mould similar-sized pieces of plasticene into different shapes e.g. flat disc, round ball.
Drop the shapes into the cylinder and see how long they take to fall to the bottom.

A more complex (but more exciting) set up of a similar phenomenon at water resistance: racing shapes through water.

Wider shapes can push more water.
The water pushing back on the shape is called water resistance, or drag. The more water that hits the object, the greater the drag. More drag will slow down an object more.

Animals that live in water will have wide feet (duck, otter, beaver) or feet with flaps that can fold out (grebe). These wide feet can push more water and move the animal through the water faster.
Canoe paddles are wide so that they can push more water to more effectively move a boat forward.
To reduce the amount of drag, boats are built with a streamlined shape so that they slide through the water more easily.
Swimmers shape their bodies to be as streamlined as possible to reduce the drag as they move through the water.

Grades taught
Gr K
Gr 1
Gr 2