NSc 105 (Fall 1996)	First Exam: 26 Sept 1996	Page 1

NSc 105 (Fall 1996)		26 Sept 1996
First Exam (100 points)	
	Name 	



This exam is closed book, closed notes.  Please note that for some sections you will have a choice of which questions to answer.  Read all instructions.  Good luck!

True/False.  Answer all questions by circling the best choice.  There are ten 'real' questions and one bogus question.  The bogus question is not to be taken internally, and will not be graded.  (1 point each; 10 points total, even though there are 11 que
stions.)

T	F	1.	Scientists must always conduct their research without preconceptions.

T	F	2.	Scientists hypothesize that there is a lot of Ôdark matterÕ in the universe because of the way galaxies, including our own Milky Way, spin.

T	F	3.	Force has units of kg m/s2

T	F	4.	Conservation of Momentum is one of NewtonÕs three Laws.

T	F	5.	Large stars have longer lives than small stars.

T	F	6.	The ÔBig SplashÕ, a theory for how the Moon was made, was turned into a popular movie starring Darryl Hanna and Tom Hanks.  Whatever.

T	F	7.	The Asteroid Belt refers to the area between Mars and Jupiter populated by small, rocky objects circling the Sun.

T	F	8	Temperature is a measure of the amount of heat in a body.

T	F	9.	Elements cannot be broken down further by chemical reactions.

T	F	10.	In scientific terms, you cannot Ôdo workÕ if nothing moves.

T	F	11	The mass of an object is independent of gravity.


Multiple Guess.  Answer all questions by circling the best choice.  (2 points each; 30 points total).

1.	For scientists, observations and experiments differ in that:
	a.	observations are harder to interpret than experiments.
	b.	observations involve manipulating some aspect of nature and observing the outcome.
	c.	experiments involve manipulating some aspect of nature and observing the outcome.
	d.	observations provide more information for testing hypotheses.
	e.	experiments provide more information for testing hypotheses.

2.	Hubble's law states that v = H d, where v is the velocity a galaxy is moving away from us in km/s, H is HubbleÕs constant, and d is the distance to the galaxy in km.  The units for H are therefore:
	a.	km.
	b.	s.
	c.	km/s.
	d.	1/km.
	e.	1/s.

Multiple Guess, conÕt

3.	A ball falls from the top of a tall building.  Its velocity is about 50 m/s just before it reaches the ground 5 seconds later.  The acceleration of the ball is therefore:
	a.	about 0.5 m/s2.
	b.	about 1 m/s2.
	c.	about 5 m/s2.
	d.	about 10 m/s2.
	e.	about 50 m/s2.

4.	A car going around a curve at a constant speed
	a.	does not accelerate.
	b.	is not being acted upon by a force.
	c.	is being acted upon by forces that cancel each other.
	d.	is accelerating.
	e.	none of the above.

5.	At which of these locations is the pull of gravity toward the center of the Earth likely to be the strongest?
	a.	On the surface of the Moon.
	b.	On the surface of the Earth.
	c.	Twenty miles above the Earth's surface.
	d.	In deep space.
	e.	The pull of gravity is equally strong in each place.

6.	The watt rating on your light bulb tells you the amount of energy your light bulb is using in joules per second.  Which of the following light bulbs is using the most energy in a day?
	a.	A 100-watt bulb that burns for half an hour a day.
	b.	A 75-watt lamp that is on for an hour a day.
	c.	A 60-watt light left on for an hour and a half a day.
	d.	A 40-watt porch light shining for two hours a day.
	e.	A 25-watt night light left on for three hours a day.

7.	A bungee jumper leaps off a platform, flies through the air, and eventually hangs motionless at the end of a cord.  At this point in time, her initial gravitational potential energy has been converted to
	a.	gravitational potential energy and heat.
	b.	kinetic energy.
	c.	heat only.
	d.	kinetic energy plus heat.
	e.	none of the above.

8.	Which of these represents the coldest temperature?
	a.	0¡ Celsius.
	b.	0¡ Fahrenheit.
	c.	0 Kelvins.
	d.	Ð100¡ Celsius.
	e.	The freezing point of pure water.


Multiple Guess, conÕt
9.	Two people on roller blades throw a ball back and forth.  After a couple of throws, they are (ignore friction)
	a.	standing where they were initially.
	b.	standing farther away from each other.
	c.	standing closer together.
	d.	moving away from each other.
	e.	moving toward each other.

10.	According to the Nebular Hypothesis, the Solar System began as
	a.	a rapidly rotating sun.
	b.	a cloud containing approximately equal amounts of all naturally occurring elements.
	c.	a cloud of dust and gas.
	d.	two comets that collided with a tremendous impact.
	e.	the Nebular Hypothesis does not address the beginning of the Solar System.

11.	A supernova is 
	a.	a rapidly rotating sun.
	b.	the normal end to stars the mass of our Sun.
	c.	the same thing as a white dwarf.
	d.	the source of elements in the universe heavier than iron.
	e.	none of the above.

12.	One of the ways that Mendeleev's writing of the periodic table fit the scientific method was that
	a.	he did not write down any part of the table until he knew what every entry would be.
	b.	once the periodic table was written, it was never changed.
	c.	Mendeleev deleted any information that did not fit his hypothesis.
	d.	only scientists can understand its organization.
	e.	it made predictions which could be tested.

13.	An element with an atomic number of 8 can be said to
	a.	be the eighth element discovered.
	b.	have four protons and four neutrons.
	c.	have eight protons.
	d.	have eight electrons in its outer shell.
	e.	have four protons and four electrons.

14.	The observation that the background microwave radiation is close to the same in all directions
	a.	is strong support for the Nebular Hypothesis.
	b.	is strong support of the Big Bang Hypothesis.
	c.	is strong support for the Big Splash Hypothesis.
	d.	indicates that the background temperature of the universe is about 300 K.
	e.	none of the above.

15.	The iron in your blood was made during
	a.	a chemical process that went on during the formation of the Earth.
	b.	the final moments in the life of a small star.
	c.	the final moments in the life of a star like the sun.
	d.	fission reactions during the Big Bang.
	e.	nuclear burning during the life of a very large star.

Short Answer. Answer 4 out of 5 questions.  If you answer more than 4 questions, only the first 4 will be graded.  There is no minimum length for an answer, and you should not need more than a sentence or two for any question.  (5 points each; 20 points t
otal).  


1.	The kinetic energy of a baseball of mass m thrown at a velocity v is _ mv2.  If the mass of the baseball itself were converted directly into energy, then according to EinsteinÕs famous equation its energy would be mc2, where c is the speed of light.  W
hich energy is greater?  Briefly explain why.













2.	Does water have a high or low heat capacity compared to, say, rock?  What is one consequence of the difference in heat capacity between water and rock? 













Short Answer, conÕt (remember, answer only 4 out of 5)

3.	Describe one way in which you count on gravity in this room, right now, while you are taking this exam.  Please be specific.













4.	Why is a new star made up primarily of hydrogen gas?













5.	Give one example of how NewtonÕs 2nd Law, F = ma, is at work in this room.



Interpretation.  Answer 1 out of the 2 sets of questions below.  (20 points).




















a.	The diagram above shows the structure of the sun.  Label the parts of the sun indicated by a,b,c on the figure.  (6 points). 
b. 	r on the figure is the radius of the sun.  Circle the best choice for the radius from the following choices.  (4 points) 

		7,000 m  or  70,00km  or  700,000 km  or  700,000,000 km  or  7 light years

c.	In which area or areas (i.e., a,b,c) is hydrogen being burned in the sun?  (2 points) 



d.	It takes about 8 minutes for the energy of the sun to get to the Earth once it leaves the sun.  Circle the best choice for the time it takes for energy to get from the center of the sun to the surface of the sun from the following choices.  (4 points)

	few seconds  or  few tens of minutes  or  few days  or  few tens of years  or  
		few tens of thousands of years

e.	What mode of heat transport dominates in the area labeled ÔcÕ on the figure? (2 points)


f.	What mode of heat transport dominates in the area labeled ÔbÕ on the figure? (2 points)


g.	The sun constantly emits a stream of particles called the solar wind, consisting primarily of ions (electrically charged atoms) of what two elements? (4 points).

Interpretation, conÕt.  Remember, answer only 1 out of the 2




















a.	Circle the Sun on the diagram.  (2 points)

b.	Indicate on the figure whether temperature increases to the left or to the right on the bottom axis.  (2 points)

c.	Indicate on the figure whether luminosity increases to the top or to the bottom on the vertical axis.  (2 points)

d.	Indicate on the figure the region known as the Main Sequence.  (2 points)

e.	What characterizes stars on the Main Sequence?  (4 points)





f.	Indicate on the figure where the Red Giants are located.  (2 points)


g.	Indicate on the figure where the White Dwarfs are located.  (2 points)


h.	Draw a line on the figure starting at the Sun that shows how the Sun will evolve when it leaves the Main Sequence.  (4 points)

Essay.  Do 1 out of the 3 questions.  You may jot down your ideas and organize your thoughts on the back of the previous page.  Please write the essay with complete sentences that make your point.  Part of the grading will be on the clarity of your presen
tation.  If you answer more than one question, only the first will be graded.  (20 points).


1.	Discuss the Nebular Hypothesis.  Your answer should include at least what it is, enough details so that someone not familiar with it could understand what it helps explain, and some evidence in support of it. 


Essay, conÕt:  Remember ... choose 1 only!

2.	Discuss either the 1st or 2nd Laws of Thermodynamics.  Your answer should include at least what the law is about and enough details so that someone not familiar with it could understand what it helps explain, and an example of something that is Ôexplai
nedÕ by the law.















Essay, conÕt:  Remember ... choose 1 only!

3.	The three modes of heat transfer include conduction, convection, and (electromagnetic) radiation.  Discuss one of these modes of heat transfer, giving an example that you can see from your seat in this classroom.