Ch 1: Representing Motion

Question 1

What is the definition of motion?

Answer 1

The change of an object’s position or orientation with respect to time.

Question 2

The path along which an object travels is called its __________.

Answer 2

trajectory

Question 3

In physics, we use model to simplify nature while still capturing the essence. One type of model is descriptive model, which….

Answer 3

…describe in the simplest terms possible.

Question 4

Explanatory models in physics have _________ power based on the laws of physics.

Answer 4

predictive

Question 5

A change of position is called a….

Answer 5

….displacement.

Question 6

Define uniform motion.

Answer 6

Motion at a constant speed in a straight line.

Question 7

Speed measures only how fast an object moves, but velocity tells us both an object’s speed and its ________.

Answer 7

direction

Question 8

The formula for velocity is…

Answer 8

Change in position/ change in time

Question 9

Scientists use a system of units called le Système International d’Unités, commonly referred to as SI Units. The SI unit of time is _____. The unit of length is _____. The unit of mass is _____.

Answer 9

second

meter

kilogram

Question 10

A one-significant-figure estimate or calculation is called an _____-__-_________ estimate.

An order-of-magnitude estimate is indicated by the symbol ~, which indicates even less precision than the “approximately equal” symbol ≈

Answer 10

order-of-magnitude

Question 11

What is a scalar quantity?

Answer 11

A physical quantity described only by a number and unit, as opposed to a vector which also has a direction.

(speed is a scalar; velocity is a vector)

Question 12

How many kilometers are in a mile?

Answer 12

1.61 km in a mile.

Question 13

When determining significant figures, the number of significant figure for multiplication, division, and powers is set by the value with….

When using addition and subtraction, it is set by….

Answer 13

…..the fewest significant figures.

….the value with the smallest number of decimal places.

Question 14

RULES FOR SIGNIFICANT FIGURES

1. All non-zero numbers ARE significant. The number 33.2 has THREE significant figures because all of the digits present are non-zero.
2. Zeros between two non-zero digits ARE significant. 2051 has FOUR significant figures. The zero is between a 2 and a 5.
3. Leading zeros are NOT significant. They’re nothing more than “place holders.” The number 0.54 has only TWO significant figures. 0.0032 also has TWO significant figures. All of the zeros are leading.
4. Trailing zeros to the right of the decimal ARE significant. There are FOUR significant figures in 92.00.
5. 00 is different from 92: a scientist who measures 92.00 milliliters knows his value to the nearest 1/100th milliliter; meanwhile his colleague who measured 92 milliliters only knows his value to the nearest 1 milliliter. It’s important to understand that “zero” does not mean “nothing.” Zero denotes actual information, just like any other number. You cannot tag on zeros that aren’t certain to belong there.
6. Trailing zeros in a whole number with the decimal shown ARE significant. Placing a decimal at the end of a number is usually not done. By convention, however, this decimal indicates a significant zero. For example, “540.” indicates that the trailing zero IS significant; there are THREE significant figures in this value.
7. Trailing zeros in a whole number with no decimal shown are NOT significant. Writing just “540” indicates that the zero is NOT significant, and there are only TWO significant figures in this value.
8. Exact numbers have an INFINITE number of significant figures. This rule applies to numbers that are definitions. For example, 1 meter = 1.00 meters = 1.0000 meters =
9. 0000000000000000000 meters, etc.

So now back to the example posed in the Rounding Tutorial: Round 1000.3 to four significant figures. 1000.3 has five significant figures (the zeros are between non-zero digits 1 and 3, so by rule 2 above, they are significant.) We need to drop the final 3, and since 3 < 5, we leave the last zero alone. so 1000. is our four-significant-figure answer. (from rules 5 and 6, we see that in order for the trailing zeros to “count” as significant, they must be followed by a decimal. Writing just “1000” would give us only one significant figure.)

8. For a number in scientific notation: N x 10x, all digits comprising N ARE significant by the first 6 rules; “10” and “x” are NOT significant. 5.02 x 104 has THREE significant figures: “5.02.” “10 and “4” are not significant.

Rule 8 provides the opportunity to change the number of significant figures in a value by manipulating its form. For example, let’s try writing 1100 with THREE significant figures. By rule 6, 1100 has TWO significant figures; its two trailing zeros are not significant. If we add a decimal to the end, we have 1100., with FOUR significant figures (by rule 5.) But by writing it in scientific notation: 1.10 x 103, we create a THREE-significant-figure value.

Answer 14

Review rules for significant figures.

Taken from:

https://ccnmtl.columbia.edu/projects/mmt/frontiers/web/chapter_5/6665.html

Question 15

Is displacement a vector?

Answer 15

Yes, displacement has both a magnitude and a direction.

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