When you suddenly stand up after lying down for a while, yourbody may not compen

Question

When you suddenly stand up after lying down for a while, yourbody may not compensate quickly enough for the pressure changes andyou might feel dizzy for a moment. If the gauge pressure of the blood at your heart is 13.3kPaand your body doesn't compensate, (a) What would the pressure be atyour head, 50.0cm above your heart? (b) What would it be at yourfeet, 1.30 x 102 cm below your heart? Hint: Thedensity of blood is 1060 kg/m3. When you suddenly stand up after lying down for a while, yourbody may not compensate quickly enough for the pressure changes andyou might feel dizzy for a moment. If the gauge pressure of the blood at your heart is 13.3kPaand your body doesn't compensate, (a) What would the pressure be atyour head, 50.0cm above your heart? (b) What would it be at yourfeet, 1.30 x 102 cm below your heart? Hint: Thedensity of blood is 1060 kg/m3.

Explanation / Answer

= 1.146 x 10^5 Pa = 1060 kg / m^3 h = 0.5 m h' = 1.3 m (a) Phead = P - g h     = 1.146 x 10^5 - 1060 * 9.8 * 0.5 = 1.09406 x 10^5 Pa (b) Now the pressure at feet Pfeet = P + g h' = 1.146 x 10^5 + 1060 * 9.8 * 1.3 = 1.281044 x 10^5 Pa

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