ASTRO 301/ 46690/ HOMEWORK 2
   
                      MONDAY  FEB 21, 2005
  
             DUE BACK ON MONDAY FEB 28, 2005 BY NOON.

 
1a. State Newton's three laws of motion.

1b. Describe the difference between mass and weight. 

1c. Using Newton's third law explain why the floor exerts a reaction
    force on your feet.


2a. State Newton's Universal Law of Gravitation.
   
2b. What is the force of gravity between the Earth and the Sun?
    Use the tables in Appendix E of  your textbook "Cosmic Perspectives",
    (3rd Edition) to find the mass of the Earth and Sun, and their separation.

2c. If the mass of the Earth and its distance from the Sun were both
    doubled, what would be the force of gravity between the Earth and 
    the Sun?

2d. How can Newton's three laws of motion and his Universal law of
    Gravitation be used to explain and generalize Kepler's three laws 
    of planetary motion?


3a. Describe the principle of conservation of momentum.

3b. A rocket of mass 100 kg is propelled upward by ejecting 500 kg of 
    gas downward at a speed of 10 km/s. What is the upward speed of the  
    rocket?


4a. Describe the principle of conservation of energy.


4b. Why is it more dangerous to jump from a tall building of height 50 m  
    than from a wall which is only a few meters high?

4c. Suppose you throw a ball high in the air and toward a window facing 
    you. The ball moves away from you as it rises high in the air and it
    then hits the window pane, smashing it into pieces. Describe the various 
    forms of energy into which the initial kinetic energy of the ball gets 
    converted into, once you have thrown the ball.


5a. State Wien's law and Stefan-Boltzmann's law for a blackbody (opaque 
    macroscopic body).

5b. What is the temperature of a blackbody whose emission peaks at a 
    wavelength of 10^-6 m?

5c. What is the energy emitted per m^2 by this body in 1 hour?

5d. Describe how electrons are arranged in an atom and how this leads
    a thin layer of gas to produce a characteristic set of emission
    lines.

5e. Under what circumstances would this thin layer of gas produce a
    characteristic set of absorption lines?