2011- 12- 12
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أكـاديـمـي
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ضرووري فيزيائيات محتاجه مساعدتكم.. بأقرب وقت -.-"
السلام عليكم...
احتاج ترجمة بعض المسائل.. جايبتها من كتاب سيراويه الانجلش,
وابي الترجمه.. جربت بقوقل يطلع لي خرابيط, ما فهمت شي .gif "(107)")
بليييز بنااااات بأقرررررب وقت محتاجته ضروري 
Q18.18 Instead of just radiating sound very softly into the surrounding air, the tuning fork makes the
chalkboard vibrate. With its large area this stiff sounding board radiates sound into the air with
higher power. So it drains away the fork’s energy of vibration faster and the fork stops vibrating
sooner. This process exemplifies conservation of energy, as the energy of vibration of the fork is
transferred through the blackboard into energy of vibration of the air.
Q18.20 Helium is less dense than air. It carries sound at higher speed. Each cavity in your vocal apparatus
has a standing-wave resonance frequency, and each of these frequencies is shifted to a higher value.
Your vocal chords can vibrate at the same fundamental frequency, but your vocal tract amplifies by
resonance a different set of higher frequencies. Then your voice has a different quacky quality.
Warning : Inhaling any pressurized gas can cause a gas embolism which can lead to stroke or
death, regardless of your age or health status. If you plan to try this demonstration in class, inhale
your helium from a balloon, not directly from a pressurized tank.
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