**FIRST HOUR EXAM**

NATURAL SCIENCE 105

HOUR EXAM ONE

6 April 2005
This is a closed book, closed note exam; calculators are not permitted (nor needed). Do all your writing in your blue book(s), putting
your name on each book you use. All questions are worth ten points unless otherwise noted. Do not hesitate to ask for clarification of
any question you may have. On this test, you may use 10 m/sec/sec as the value of the acceleration due to gravity.

1.

a) Define density. If you use an equation, be sure that you state the meaning of each symbol you use. (5)

b) Describe the processes by which you determined the density of common objects such as nails. Explicitly describe what
measurements you took and how you took them. (5)

c) What was the greatest source of error in your density measurements, and how might you redo the
experiment to reduce the impact of that source of error? (10)

2.

a) Define each of the terms: atomic number, atomic mass, isotope. (10)

b)What property of an atom determines the type of atom it is (i.e., what property distinguishes hydrogen from helium from lithium,
etc.) (5)

c) In a certain type of nuclear decay, a neutron in the nucleus transforms into a proton (which remains in, and is a part, of the new
nucleus). The nucleus ^{14}C_{6} is a nucleus that manifests this type of nuclear process. What is the nucleus that
will be formed after a
neutron in ^{14}C_{6} transforms into a proton? (The atomic numbers of the following atoms are shown along with the
chemical symbols of those
atoms, this information may be helpful in answering this question) Your answer must consist of an atomic number, atomic mass, and
chemical symbol.

H 1; H3 2; Li 3; Be 4; B 5; C 6; N 7; O 8; F 9; Ne 10

3. Define each of the following terms: speed, velocity, acceleration.

4. How do average speed and instantaneous speed differ. Write the equation (identifying clearly the meaning of
each symbol used) for average speed.

5. Suppose a ball starts from rest and rolls down an inclined plane of length one meter in a time of 2 seconds. Showing your work
(and units) clearly, calculate each of the following:

a) average speed

b) final instantaneous speed

c) acceleration

6. Suppose the ball in the problem above was dropped from rest and allowed to
fall straight down in the Earth's gravitational field. Neglecting the effects of air friction, calculate each of the following (showing
clearly your work and units):
a) The final instantaneous speed after 3 seconds of flight.

b) The average speed for the three second time interval.

c) The total distance traveled in three seconds.

7. Suppose the ball in problem five is on a very long track, but has the same acceleration as you calculated in problem 5
above. How far would this ball travel at this acceleration if it rolled for four seconds. Explain your answer and/or show your work.

8. What is the difference (if any) between mass and weight?

9. Suppose you place a ball in the middle of a wagon that is initially at rest and then abruptly pull on the wagon (with a
perfectly horizontal force). Describe the motion of the ball relative to a) the wagon and b) an observer standing on the sidewalk.

10. A swimmer directs his/her motion directly across a river. The swimmer's speed in quiet water is 3 mi/hr. The river current
flows exactly parallel to the banks of the river at 4 mi/hr. Showing your work clearly, calculate the following:

a) What is the total speed of the swimmer in the water?

b) If the river banks are 6 mi apart, how long does it take the swimmer to cross the river?

c) How far downstream does the swimmer land compared to the position of the starting point?