As discussed in Section 13.3 , a person’s percentage of body fat can be estimated by weighing the person both in air and underwater, from which the average density ρ avg can be calculated. A widely used equation that relates average body density to fat percentage is the Siri equation , % body fat= (495/ ρ avg – 450, where ρ avg is measured in g/cm 3 . One person’s weight in air is 947 N while his weight underwater is 44 N. What is his percentage of body fat?
As discussed in Section 13.3 , a person’s percentage of body fat can be estimated by weighing the person both in air and underwater, from which the average density ρ avg can be calculated. A widely used equation that relates average body density to fat percentage is the Siri equation , % body fat= (495/ ρ avg – 450, where ρ avg is measured in g/cm 3 . One person’s weight in air is 947 N while his weight underwater is 44 N. What is his percentage of body fat?
As discussed in Section 13.3, a person’s percentage of body fat can be estimated by weighing the person both in air and underwater, from which the average density ρavg can be calculated. A widely used equation that relates average body density to fat percentage is the Siri equation, % body fat= (495/ρavg – 450, where ρavg is measured in g/cm3. One person’s weight in air is 947 N while his weight underwater is 44 N. What is his percentage of body fat?
5. A potential divider circuit is made by stretching a 1 m long wire with a resistance of 0.1 per cm
from A to B as shown.
8V
A
100cm
B
sliding contact
5Ω
A varying PD is achieved across the 5 Q resistor by moving the slider along the resistance wire.
Calculate the distance from A when the PD across the 5 Q resistor is 6 V.
4. A voltmeter with resistance 10 kQ is used to measure the pd across the 1 kQ resistor in the circuit
below.
6V
5ΚΩ
1ΚΩ
V
Calculate the percentage difference between the value with and without the voltmeter.
1.
A 9V battery with internal resistance 5 2 is connected to a 100 2 resistor. Calculate:
a. the Power dissipated in the 100 2 resistor
b. The heat generated per second inside the battery.
C.
The rate of converting chemical to electrical energy by the battery.
2. A 230 V kettle is rated at 1800 W. Calculate the resistance of the heating element.
Chapter 13 Solutions
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