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

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
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
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 2
This is the end of the preview. Sign up to access the rest of the document.

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?...
View Full Document

This note was uploaded on 11/03/2009 for the course PHYS100 100 taught by Professor Lioudmila during the Spring '09 term at UBC.

Page1 / 2

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

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online