Question

1. A 300 W immersion heater is used to heat 400 g of water from 10 ⁰C to 80 ⁰C. About how many minutes did this take?
   1. 5 min
   2. 3.5 min
   3. 2 min
   4. None of the above is correct
2. As blood passes through the capillary bed in an organ, the capillaries join to form venules (small veins). If the blood speed increases by a factor of 4.00 and the total cross-sectional area of the venules is 9.5 cm², what is the total cross-sectional area of the capillaries feeding these venules? How many capillaries are involved if their average diameter is 10 micrometers?
   1. 38 cm² and 48,383,103 capillaries
   2. 40 cm² and 50,000,000 capillaries
   3. 310 cm² and 45,000,000 capillaries
   4. None of the above is correct
3. Hoover Dam on the Colorado River is the highest dam in the United States at 221 m, with an output of 1300 MW. The dam generates electricity with water taken from a depth of 150 m and an average flow rate of 700 m³/s. (a) Calculate the power in this flow. (b) What is the ratio of this power to the facility’s average of 680 MW?
   1. 955.5x10⁶ W and 2.12
   2. 1.029x10⁹ W and 1.51
   3. 955.5x10⁶ W and 1.41
   4. None of the above is correct
4. Calculate the retarding force due to the viscosity of the air layer between a cart and a level air track given the following information—air temperature is 20 ⁰C, the cart is moving at 0.500 m/s, its surface area is 3x10^-2 m², and the thickness of the air layer is 5x10^-5 m² . What is the ratio of this force to the weight of the 0.300-kg cart?
   1. 3.02x10^-3 N and 1.03x10^-3
   2. 1.03x10^-3 N and 1.5x10^-3
   3. 1.2x10^-2 N and 1x10^-3
   4. None of the above is correct

Answer 1

PROBLEM 1:

The mass of the water is

The initial and final temperature is

The heat capacity of the water is

The heat required to increase the temperature is

The power delivered by the heater is

So, the time required by the heater is

So, the correct option is d) none of the above is correct.

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