Name _______________ Box # ______ Score _________ September 16, 1999

Text:P. Zitewitx,, Physics , Principles and Problems, Glencoe/McGraw-Hill (1999)

In all numerical questions below show how you obtained your result. Answers without justification will be given zero points.

1. (6) Describe at least four common elements of the Scientific Method. What should you say to some one who tells you that science has proved a certain idea to be true?

observation, looking for patterns, building models, making predictions, doing more experiments, publishing

Science cannot prove anything to be true, it tests models and can show them false. A particular model guides the way we think about nature when it has been shown consistent with nature by many experiments.

2. (5) What would you tell your parents that physics is? Specifically how does it relate to the "laws of the universe"?

Physics is a study matter and energy, a search for the simplest and fewest laws to explain everything in the universe.

3. (6) What are the SI units for the following quantities?

a) mass kilogram      b) length meter

c) time second d) displacement meter

e) velocity meter/second f) acceleration meter/second²

4. (9) Solve the following problems and express the results in scientific notation using the correct number of significant digits.

a) 9.04376x10¹⁵ m / 3.06 x 10^-6 s = 2.96x10²⁴ m/s

b) 7.32 km/s + 2.64 mm/s = 7.32x10³ m/s

c) .003802 - .00381092 = -.000009

5. (4) Give the name of the prefixes for the following factors of powers of ten.

a) 10⁶ mega b) 10^-2 centi

c) 10^-3 milli d) 10³ kilo

6. (4) Express in centimeters the two measurements indicated in figure 1 being careful that the number of significant digits represents correctly the precision of the measurements.

a) 88.4 cm

b) 88.43 cm

7. (15) The position of a lab cart traveling over a time of five seconds is shown in Table 1.

a)(5) Plot the points and draw the best straight line through them.

b)(6) What are the values of the slope and intercept of this straight line?

slope = rise over run = (1.48 m -.26 m) / (5 s - 1 s) = .29

extrapolate the graph to the origin (0,0) gives the intercept = .02 ( zero is okay).

c)(4) Write an equation that expresses the position,d, as the dependent variable in terms of the independent variable, t.

d(t) = .29 m/s x t where x means multiplication.

8. (7) A car is moving northward so that at a time of 22 seconds it's position is 436 m south of the origin. At a time of 26 seconds the car's position is 356 m south of the origin.

a) Using a complete sentence define in words the average velocity.

Average velocity is equal to the change in the position vector divided by the time the change occurred.

b) What is the average velocity of the car over this time period?

Change in position = d_f - d_i = -356 m - (-436 m) = 80 m, Change in time = 4 s.

Average velocity = 80 m / 4 s = 20 m/s

9. (6) What are the two characteristics of a vector quantity? List four different physical quantities that are vectors.

size or magnitude and direction. displacement, position, velocity, acceleration, force

10. (6) In a complete sentence state what an operational definition is. State an operational definition of constant velocity of an object whose motion is recorded on a fixed video recorder.

An operational definition is a statement of a procedure to obtain a measured value of the quantity. For a fixed video camera an object moving with a constant velocity will have a constant displacement of the object from one frame to the next.

11. (5) Lisa straps on a harness and does a bungee jump. One end of the cord is fastened to the platform that she is standing on, the other is connected to her harness. The cord is 5 m long and the platform is 15 m above the ground. Draw a motion diagram of her vertical motion from the time that she steps off the platform until she stops moving downward at a distance of 5 m above the ground.

I will draw the diagram on its side.

12. (5) Give an example of an object that has a negative position, a positive velocity and a negative acceleration. Is the object speeding up or slowing down?

A car is south of the origin, moving northward and applying its brakes to decelerate (accelerate southward).

The car is slowing down.