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A man uses a dog whistle to call his dog - Edexcel - GCSE Physics - Question 4 - 2014 - Paper 1
Question 4
A man uses a dog whistle to call his dog. The whistle uses ultrasound. (i) The dog can hear the whistle but the man cannot. Explain why the dog can hear the whistle... show full transcript
Worked Solution & Example Answer:A man uses a dog whistle to call his dog - Edexcel - GCSE Physics - Question 4 - 2014 - Paper 1
Step 1
Explain why the dog can hear the whistle but the man cannot.
Answer
The dog can hear the whistle because the frequency of the sound produced by the dog whistle is higher than 20,000 Hz, which is within the hearing range of dogs. Humans, however, have a limited hearing range (typically up to 20,000 Hz), so they cannot hear sounds above that frequency, making the dog whistle inaudible to them.
Step 2
Calculate the speed of ultrasound.
Answer
To calculate the speed of ultrasound, we use the formula:
ext{Speed} = rac{ ext{Distance}}{ ext{Time}}-
Substitute the values:
- Distance = 140 m
- Time = 0.42 s
-
Calculation:
ext{Speed} = rac{140 ext{ m}}{0.42 ext{ s}} \\ ext{Speed} = 333.33 ext{ m/s} -
Therefore, the speed of ultrasound is approximately 330 m/s.
Unit: m/s.