Copy of 5BL Lab 1 Assignment Submission Template - W24v2

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University of California, Los Angeles *

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Mechanical Engineering

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Apr 3, 2024

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5±L Lab 1 ²ssignment Waseem Shindy, 1/22, °5, 1 <URNK] SPVS]VSkjURNKLI ALILIVS]TQ x_nmpj jNKkjfg_]kjNKkj _] NKAJUR kj[VSLINK kjAsruNK mlURVSkj Akj A +±" SPVS[NK A]LI nmpfg[_ALI VSml ml_ x_nmpj #jALINKkjJ_fgNK AkjkjVSTQ]\NK]ml

²ctivity 1 Response : Measure the temperature of the environment (ambient temperature), the human body (both forehead and under the tongue), and two other objects in the room. Record this information in both and , and group the items into a category of either being in or out of equilibrium with the environment. Using the human body as the system, state the direction of heat flow between the body and the environment and explain why heat flows in this direction. ³nvironment: 22.2 ´ or 71.96 µ Out of ³quilibrium ¶n ³quilibrium µorehead: 96.7 µ ±ackpack 71.8 µ Tongue: 36.3 ´ Phone 76.5 µ With the body as the system, the heat will flow from the body to the environment, heat flows in this direction because of the second law of thermodynamics, causing the heat to flow in this direction

²ctivity 2 Response: Use the ¶R temperature gun to measure the temperature of your hands both before and after vigorously rubbing them together. ±ompare the temperature difference (if any) before and after, and relate this to how the temperature change is providing information about how energy is changing form. Record how long it takes for your hands to get back to thermal equilibrium, and explain how this occurs. Temperature of hands before: 90.4 µ Temperature of hands after: 97.5 µ 1 min 56 seconds back to equilibrium when comparing the temperature difference between before and after rubbing hands, we can see that the hands increased by 7 degrees. This is a clear sign of the chemical energy stored in our bodies, turning into thermal energy from the friction of our hands rubbing together. ¶t took roughly 2 minute for our hands to reach thermal equilibrium again. This is once again due to the transfer of heat from hot to cold as stated in the second law of thermodynamics.

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²ctivity 3 Response: ²s an investigation of scientific question ±, consider an object that is not the human body, but that also has a consistently higher temperature than the environment. ±ased on your results from activity 2, describe how you would expect its thermal energy and temperature to change with time. ·ow is it able to stay at a hotter temperature than the surroundings, even though heat is constantly flowing? °iven that energy is conserved when considering an entire system, what is the energy flow process throughout the entire system that allows the hot object to stay hot? Now, relate this to the temperature measurements taken of the human body, and explain how our human body is able to consistently maintain a hotter temperature than the environment. We would expect said object to drop temperature to the temperature of the environment. Unless, that object is constantly converting some other form of energy (chemical, electrical, etc) into thermal energy to maintain thermal equilibrium The energy flow process is from other forms of energy turning into thermal energy to maintain the hot temperature. When we measured the human body, it was 25 degrees µ hotter than the environment. it is able to maintain that temperature, via the conversion of chemical energy (stored and consumed as food) into thermal energy

²ctivity 4 Response: Use either a human body, electronic devices, and/or light bulbs to capture two (2) images with the µL¶R device that each indicate a difference in temperature between two or more objects. ´apture the µL¶R images with your phone camera and paste them here. µor each image: ²escribe the heat flow between different objects visible, and indicate how these temperature differences were created and/or maintained by energy changing forms. *Label the hottest/coolest objects in your images. (¶f necessary, provide additional diagrams to supplement your explanations for clarity.) hottest coolest The picture on the left is my laptop charger, plugged into an outlet on the cool lab bench. The heat is evidently flowing from the hot charger which is hot due to the electricity running through it, and the cool lab bench which is cooled by the air of the environment. The picture on the right is my keys on top of my laptop. The heat is flowing from the much warmer laptop screen to the much cooler environment around it and the keys that ¶ placed on it. The keys were cooled by the environment, before ¶ placed them on my laptop.