Subject: The consequences of Earth’s rotation

Target group

1st‑grade student of high school and technical school (basic programme)

Core curriculum

II. Earth in the Universe: Earth as a planet, consequences of Earth's movements, celestial bodies, Solar System, construction of the Universe.

Student:

2 ) explains the characteristics of the Earth's movements and characterizes their consequences, taking into account the Coriolis force;

Purpose of the lesson

The student explains the phenomenon and consequences of the Earth's rotation.

Success criteria

• you will explain the concept of solar time and explain the relationship between solar time and Earth's rotation;

• you will talk about the Coriolis force and explain the relationship between the Coriolis force and the Earth's rotation;

• you will determine the direction of the Coriolis force on a moving body;

• you will give examples of the effects of the Coriolis force.

Key competences

• communicating in the mother tongue;

• communicating in foreign languages;

• mathematical competence;

• IT competences;

• learning to learn.

Methods / forms of work

• problem methods: directed conversation, didactic discussion;

• exhibiting methods: presentation;

• programmed methods: using a computer, using an e‑textbook;

• practical methods: subject exercises.

• individual and collective work.

Teaching resources

• computers with internet access;

• multimedia resources contained in the lesson „Consequences of the Earth's rotation” in the e‑textbook;

• interactive whiteboard / blackboard, marker / chalk.

Lesson plan

Introduction

1. During the course of the lesson, the teacher determines the purpose of the lesson, informing students about its planned course.

2. A reminder of the information about the Earth's rotation. The teacher asks questions about the consequences of the rotational movement of our planet, known from previous lessons. Volunteers or persons indicated by the teacher, in turn, tell about such consequences as the apparent movement of the Sun on the celestial sphere, and consequently - also the sequence of day and night and the flattening of the globe at the poles. The teacher completes the students' statements by introducing the notion of the sunny (local) time associated with sun‑raising above a given meridian.

Realisation

1. Introduction of the concept of Coriolis force, created exclusively in a rotating system. The lecturer discusses the illustration attached to the „Consequences of the Earth's rotation” lesson in the e‑textbook explaining that the Coriolis force causes the movement path of the moving objects in the northern hemisphere to the right and the left in the southern hemisphere.

2. Individual student work. Students perform exercise 1 and exercise 3 from the lesson in abstract, as well as an interactive exercise such as the one‑choice question. The teacher checks to see if all students are doing the job properly and helping students who have problems.

3. The teacher's observation of the observable effects of the Coriolis force, such as:

• stronger water washing through the right river banks in the northern hemisphere and left banks in the southern hemisphere;

• difference in the direction of cyclone rotation in the northern and southern hemisphere. The lecturer discusses the interactive illustration depicting the formation of cyclones. He or she draws attention to the fact that in the northern hemisphere the cyclones rotate in a counter‑clockwise direction and in the south - in a clockwise direction.

Summary

The last stage of the lesson is a short summary to systematize and consolidate the message, clarify any ambiguities and complete the notes.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

The consequences of Earth’s rotation

We know that the Sun’s apparent motion on the Celestial sphere is caused by Earth’s rotation. However, this movement carries on several other consequences for our planet, geographical environment, and all living beings, including humans. One of the most obvious is the succession of day and night. For some time, a part of Earth is turned towards the Sun, resulting in a day. Then Earth turns away from the Sun and night falls in the shadowed area. At the same time, another part of the planet turns to the Sun and the day starts there.

Another consequence of Earth’s rotation is the existence of solar time. At the same moment, on one of the meridians there is a solar noon, while on the opposite side of the planet – midnight, and on the other ones, all the other times during the day or night cycle.

A difficult to observe, but the scientifically proven consequence of Earth’s rotation is also a small flattening at the poles, resulting from the centrifugal force, causing Earth not to have a spherical shape.

In a rotating system, which is Earth, the trajectory of the body moving on the surface deviates from the straight line, because the body is under the effect of the so‑called Coriolis force. This force causes the trajectory of the moving objects in the Northern Hemisphere to turn right, and turn left in the Southern Hemisphere. Rivers, winds and currents as well as ships, airplanes and other objects in motion are subject to the Coriolis force. Of course, this force does not work on objects that are at rest.

This phenomenon can be explained by the example of large rivers, whose right banks in the Northern Hemisphere and the left banks in the Southern Hemisphere are more washed off by water.
If the river flows from south to north (in the Northern Hemisphere), the water in it moves from the area where the linear velocity of the rotating (from west to east) Earth is greater, to the place where the linear velocity is smaller. But the water is not rigidly connected to the Earth and, running north, retains its greater linear velocity, turns from west to east, which in result causes a stronger flow on the right (eastern) shore.
If the river runs from north to south (in the Northern Hemisphere), it means that the water in it moves with a smaller linear velocity from the area to a place with a higher linear velocity. It tries to keep the velocity lower, but the river banks move faster (from west to east). So now the right (west) bank of the river will „push” the water, and the water, as a result, will wash it off more.
In the Southern Hemisphere, the phenomenon occurs analogously, only in reverse.

Like the water in larger rivers, even the winds in the Northern Hemisphere will be pushed to the right, and to the left in the Southern Hemisphere. Another consequence of the Coriolis force is the direction of air rotation in cyclones. In the Northern Hemisphere, they rotate counter‑clockwise and clockwise in the Southern Hemisphere.