1. Lightning is seen 3 seconds before a thunder. How far away has the thunder
taken place? Take velocity of the sound = 340 m/s.

2. Ultrasonic waves are used to locate a sunken ship under the sea. If the reflected wave is received by the receiver after 12 seconds, how far is the ship
under water? Take the velocity of sound in water as 1450 m/s.

3. How is SONAR method different from RADAR method?

4. State three uses of ultrasound.

5.Exlain the following:
(a) Sounds are heard clear at night.
(b) Nocturnal animals can find their prey in darkness.

See explanation

Explanation:

1) We know that speed = distance/time

distance = speed * time = 340m/s * 3 s= 1020 m

2) For sound waves, v =2s/t

where s is the distance traveled and t is the time taken.

s = vt/2 = 1450 m/s * 12 s/2 = 8700 m

3) According to Minkoff, 1991, "Radar systems operate using radio waves primarily in air, while sonar systems operate using sound waves primarily in water"

4) It is used for medical diagnosis

It is used in making the automatic door opener

It is used to detect invisible flaws in products

5

a) At night, sound is refracted towards the earth because the air near the surface of the earth is cooler. As a result of this, sounds are heard clear at night.

b) Nocturnal animals possess greater number of rods which receives more  light even in the dark. This enables the animals to see their prey even in darkness. They have larger eyes compared to their body size. Their eyes and their pupil widen in the dark to allow more light to pass through.

found in the nucleus

has mass of one amu

another example of kinetic energy would be,

kinetic energy   >     moving energy

answer   >   letter choice (c),   a hammer falling off a table.

hope that !                                         : )