Page 25 - Science and Technology Std 3

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Activity 1 To investigate how sound travels in the air

Materials a bell and a piece of iron
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Procedure

(i) Observe when the school bell rings.
(ii) From which direction are the pupils coming to the
assembly point?
(iii) To which direction do the sound waves go?

(iv) Write down what you observe and hear.

When the bell rings, sound waves spread in all directions.
Pupils hear the sound and assemble from all directions. The

sound travels by spreading in air through waves.

Uses of sound energy
1. For communication as in talking, calling and crying.

2. For entertainment such as listening to music.

3. For alarm or alert such as ambulance, police, fire and

horns.

4. Used by bats to navigate and find food.

Reflection of sound

Sound bounces back when it meets an obstacle or a solid
body. This is a reflection of sound. A solid body can be a wall
or a rock. A reflected sound is called an echo.

Activity 2 To produce an echo

Material Empty room

Procedure

(i) Get into an empty room and shout “hello”.
(ii) What do you hear?

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PROPERTY OF UNITED REPUBLIC OF TANZANIA GOVERNMENT
Ministry of Education, Science and Technology
Science and Technology 3.indd 18 03/08/2019 11:01