When boiling water a hot plate takes an average of 8 minutes [min] and 55 seconds [s] to boil 100 milliliters [mL] of water. Assume the temperature in the lab is 75 degrees Fahrenheit [°F]. The hot plate is rated to provide 283 watts [W], If we wish to boil 100 milliliters [mL] of acetone using this same hot plate, how long do we expect the process to take? Acetone has a boiling point of 56 degrees Celsius [°C], The specific heat capacity of water is 4.18 joules per gram degree Celsius [J/(g °C)]. Acetone has a specific gravity of 0.785 and a specific heat capacity of 2.15 joules per gram degree Celsius [J/(g °C)]. [ Hint: You must determine the efficiency of the hotplate.]
When boiling water a hot plate takes an average of 8 minutes [min] and 55 seconds [s] to boil 100 milliliters [mL] of water. Assume the temperature in the lab is 75 degrees Fahrenheit [°F]. The hot plate is rated to provide 283 watts [W], If we wish to boil 100 milliliters [mL] of acetone using this same hot plate, how long do we expect the process to take? Acetone has a boiling point of 56 degrees Celsius [°C], The specific heat capacity of water is 4.18 joules per gram degree Celsius [J/(g °C)]. Acetone has a specific gravity of 0.785 and a specific heat capacity of 2.15 joules per gram degree Celsius [J/(g °C)]. [ Hint: You must determine the efficiency of the hotplate.]
Solution Summary: The author calculates the time taken by the process to heat the acetone.
When boiling water a hot plate takes an average of 8 minutes [min] and 55 seconds [s] to boil 100 milliliters [mL] of water. Assume the temperature in the lab is 75 degrees Fahrenheit [°F]. The hot plate is rated to provide 283 watts [W], If we wish to boil 100 milliliters [mL] of acetone using this same hot plate, how long do we expect the process to take? Acetone has a boiling point of 56 degrees Celsius [°C], The specific heat capacity of water is 4.18 joules per gram degree Celsius [J/(g °C)]. Acetone has a specific gravity of 0.785 and a specific heat capacity of 2.15 joules per gram degree Celsius [J/(g °C)]. [Hint: You must determine the efficiency of the hotplate.]
To heat potatoes, you use a microwave with an output power of 780 watts [W]. The microwave has "pre-set" cook buttons. The "potato" button will cook a 0.625 pound-mass [lbm] potato by heating the potato from room temperature (assumed to be 68 degrees Fahrenheit [°F]) to 425 degrees Fahrenheit [°F]. The specific heat of a potato is 3.4 kilojoules per kilogram kelvin [kJ/(kg K)]. What is the length of time the "pre-set" button is programmed to operate in units of minutes [min]?
A robotic rover on Mars finds a spherical rock with a diameter of 8 centimeters [cm]. The rover picks
up the rock and lifts it 25 centimeters [cm] straight up. The rock has a specific gravity of 4.75. The
gravitational acceleration on Mars is 3.7 meters per second squared [m/s²]. If the robot's lifting arm
has an efficiency of 35% and required 10 seconds [s] to raise the rock 25 centimeters [cm], how
much power in units of watts [W] did the arm use?
One mole of an ideal gas, initially at 30 [°C] and 1 [bar], is changed to 130 [°C] and 10 [bar] by two different mechanically reversible processes:
• The gas is first heated at constant volume until its temperature is 130 [°C], then it is compressed isothermallyuntil its pressure is 10 [bar].• The gas is first compressed adiabatically; then it is heated isobarically to 130 [°C] and 10 [bar].
Calculate Q, W, ΔU, and ΔH in [J] for each case. Take Cp = 5/2R and Cv = 3/2R.
Chapter 8 Solutions
Thinking Like an Engineer: An Active Learning Approach (4th Edition)
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8.01x - Lect 27 - Fluid Mechanics, Hydrostatics, Pascal's Principle, Atmosph. Pressure; Author: Lectures by Walter Lewin. They will make you ♥ Physics.;https://www.youtube.com/watch?v=O_HQklhIlwQ;License: Standard YouTube License, CC-BY