Midterm 3 - 1) ultraviolet lights; 2) visible lights; 3) at...

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Q1 (1pt) A block with an initial velocity 10m/s comes a stop on a frictional surface. Which of the following is true? 1) The total of the mechanical energy of the block and thermal energy on the surface is not conserved because the frictional force is an external one. 2) The mechanical energy is conserved because the frictional force is an internal force between the surface and the block. 3) The total heat generated before it stops depends on the magnitude of the frictional force. 4) The amount of the heat generated is equal to the initial kinetic energy the block has. Q2 (2pt) In a lecture demo, you see that a ball released from 1.25m above the ground reaches the floor with speed v before it bounces back to a maximal height h . Assume that the ball loses 20% of it mechanical energy after hitting the floor. v and h should be 1) v = 5m/s and h = 0.75 m; 2) v = 2.5m/s and h = 0. 9 m; 3) v = 2.5m/s and h = 1.05m; 4) v =5m/s and h = 1m. Q3 (1pt) The universe at temperature 2.7K mainly radiates
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Unformatted text preview: 1) ultraviolet lights; 2) visible lights; 3) at infrared wavelengths; 4) microwaves. Q4 (3pts). A marine biologist, Lisa, wants to know how much energy emperor penguins that live in Antarctic get from food every day. Lisa observes that penguins must maintain their body temperature at 38 C in order to survive. Can you help Lisa on this? Assume a penguin has a layer of 2cm thick feathers with a thermal conductivity of 0.03 W / m K. 1m 0.4m Q5 (3pts) A spaceship is powered by solar energy. The solar panel area A is 20 m^2. The solar constant S near the earth is approximately equal to 1367 W/m^2. a) (2pts) Estimate the normal output power of the solar battery assuming the efficiency e is 25% and the panel is always directly facing the Sun. b) (1pt) The spaceship needs twice the output power estimated in a) to accomplish another mission and the solar panel needs to be upgraded. How big the panel area A should be for the new mission?...
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Midterm 3 - 1) ultraviolet lights; 2) visible lights; 3) at...

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