Modeling Prompt: Swept Away

In Class Launch

Use after Unit 6, Lesson 19.

Ask students if they have ever been to a beach at the ocean when the tide was coming in or going out. Ask them to describe the experience. At high tide, the level of the water goes up and so the water comes further up the beach and at low tide the level of the water goes down and leaves more of the beach exposed. When the tide is not at its highest level, it is often possible to observe where the high tide reaches by looking at the debris (for example, seashells, algae, and driftwood) on the beach.

Consider asking students if they know what causes the tides, making a list of different ideas they propose. Some ideas may include

  • the rotation of the earth

  • the Sun (gravity or heating)

  • the Moon (gravity)

The last of these will turn out to play a major role and this should be brought out in the discussion once students have produced their model for the tides.

Once students have modeled the given data, they will be asked to check their model's predictions for later dates. If they use the provided data of July 4th and 5th of 2018, be prepared to give them the data for July 11th and 12th to check their model. The high tides on July 11th occur near 10:00 a.m. and p.m. and the low tides occur near 4:00 a.m. and p.m. The times for the July 12th tides are about an hour later. The high tides are close to 11 feet and the low tides average close to 1 foot below the mean lower low water level.

Blackline Masters

  • Modeling Rubric
  • Advice on Modeling
  • July 11-12 Data



  • HSF-BF.B.3
  • HSF-IF.B.4
  • HSF-IF.C.7.e
  • HSF-TF.B.5