Scientific Method/Measurement/Kinematics Test Review

Question 1

What is the scientific method?

Answer 1

A process by which the scientific community uses a set of techniques to investigate phenomena.

Question 2

List the steps of the scientific method.

Answer 2

1. Problem (ask a question about something/a problem you observed)
2. Construct a hypothesis (an educated guess about your observation)
3. Test hypothesis by experiment (used to see if hypothesis is right or not; data is also collected about your experiment)
4. Analayze your data (to see if hypothesis is true)
5. Draw conclusion

Question 3

What do you do if your hypothesis is wrong?

Answer 3

Think and try another hypothesis (start steps again [until you get a true hypothesis]). If it were true, you would report your results.

Question 4

Explain SI units.

Answer 4

Every measurement in physics is made up of a unit and quantity (without a unit, a measurement would make no sense). SI units are a system of standard units agreed upon [by the scientific community] and used for the representation of measurement and quantities. Divided into two: fundamental units and derived units.

Question 5

What are fundamental units? What are derived units?

Answer 5

Fundamental units are the base units (every other unit depends on/is made up of these). All other units are called derived units (ex. Joule, Watt, Volt, Newton, etc,).

Question 6

What’s a prefix?

Answer 6

Prefixes go before units: SI units also consist of a set of prefixes used to represent smaller/larger quantities.

Question 7

List the seven fundamental units with their corresponding quantities.

Answer 7

1. Meter (m) - measures distance/length (ex. meter stick, ruler, measuring tape)
2. Kilogram (Kg) - measures mass (ex. triple beam balance, digital balance)
3. Second (s) - measures time (ex. stopwatch/clock)
4. Kelvin (K) - measures temperature (ex. thermometer)
5. Ampere (A) - measures electric current (ex. ammeter)
6. Mole (mol) - measures amt. of substance (ex. hygrometer)
7. Candela (Cd) - measures luminous intensity (ex. photometer)

Pneumonic: My Kid Sister Kicks At My Car

Question 8

What are uncertainties/errors in measurement?

Answer 8

Occurs when there’s a difference between an obtained value and the perfect value. Two types: systematic and random.

Question 9

What is systematic error?

Answer 9

Caused by any factor that consistently affects your experiment. Sometimes called “zero error”. Points tend to be organized but distributed (disturbed?) in some direction (data shifted away from the origin). Cannot be reduced by repeated reading. Can occur in every equipment that has a needle.

Sources: Instrument with zero error, wrongly calibrated instrument, poor eye sight..

Question 10

What is random error?

Answer 10

Caused by any factor that affects the measurement for a variable: by chance (unpredictable; not deliberate). Pushes plotted data up and down randomly on a graph (points not organized). Always present; cannot be completely removed. Can be reduced by repetition (of readings).

Sources: Observer being less-than-perfect, observer’s change of mood, readability of instrument, change in surroundings/weather.

Question 11

What is precision?

Answer 11

A measure of how reproducible an experiment is. Precise data is uniform, but may not represent the actual result. Reveals something about quality of instrument (experiment has a lot of systematic error).

Question 12

What is accuracy?

Answer 12

A measure of how closely the experimental results agree with the actual result. Results/Data may not be uniform, but very close to accepted value (has a lot of random error).

*Data that is both precise and accurate - Points close to each other, but also at the spot.

Question 13

What is mechanics?

Answer 13

Branch of physics that deals with motion and its causes. Divided into two: kinematics (deals with description of motion, describes two kinds of motion: one-dimensional motion [ex. a car moving in a straight line, a rocket going straight up, dropping of an object, etc.] and two-dimensional motion) and dynamics (deals with causes of motion [forces]).

Question 14

What is motion?

Answer 14

Change in position relative to a frame of reference (point from which movement started).

Qualities used to describe motion:
- Speed
- Distance
- Velocity
- Acceleration
- Momentum
- Displacement
  etc.

Question 15

What is distance?

Answer 15

How far one travels to get to a certain destination. Scalar quantity (no direction involved).
ex. 40km, 20m, etc.
Unit: meter (m)
Symbol: d or x

Question 16

What is displacement?

Answer 16

Distance from the starting to the destination in a certain direction (vector quantity); change in position/difference between final and starting point (in a straight line [must be so for it to be displacement]). Can be negative (backwards, left, downwards, South, West) or positive (Right, upwards, East, forward).
ex. 30m West, 50m SE, etc.
Unit: meter (+ direction)
Symbol: d or x
Final position - Initial position

Question 17

What is speed?

Answer 17

Distance covered by an object per unit time (scalar). Slope of a distance-time graph represents speed (rise/run = distance/time = speed).
speed = distance/time
unit: m/s
Symbol: s or v

Question 18

What is velocity?

Answer 18

Displacement of an object per unit time (vector); speed in a certain direction (change in position per unit time). Slope of a displacement-time graph represents velocity (slope = displacement/time = velocity).
Velocity = Displacement/time
Velocity = Change in position/time
unit: m/s (+ direction)
Symbol: V

Question 19

Interpreting distance-time/displacement-time/velocity-time graphs . . .

Answer 19

The slope and shape of a graph determines its interpretation:
Slope could be speed, velocity, or acceleration (depending on y-value).
Straight line = constant
Curve = not constant
Line goes up = positive
For a horizontal line, slope = speed = 0
*Object is not moving; distance is unchanging
*Velocity is unchanging, so acceleration is unchanging

Question 20

What is average speed?

Answer 20

Total distance/Total time

Question 21

What is average velocity?

Answer 21

Total displacement/Total time

Question 22

What is instantaneous speed?

Answer 22

Speed at a certain point in time (ex. speedometer - changes rapidly [your speed is constantly changing]). Inferred: speed was changing. To calculate, a tangent must be drawn. Graph must be a curve (slope is changing). Tangent must cover at least half of the graph and touch the point exactly (to find the slope in physics, a triangle must be drawn [rule for constructing a slope]).

Instantaneous speed = change in y/change in x

Question 23

What is acceleration?

Answer 23

Defined as the rate of change of velocity (vector). The slope of a velocity-time graph represents acceleration.
a = change in v/change in t
a = final velocity - initial velocity/change in t
unit: m/s squared

Conditions under which an object is said to be accelerating:

• velocity increases
• velocity decreases
• direction changes

Question 24

What is motion with constant acceleration?

Answer 24

Motion whose velocity (displacement) increases by equal amount over the same amount of time (proportionally). Also called motion with uniform acceleration (ex. an object falling in a straight line in absence of air resistance [free fall], projectile motion [absence of air resistance], motion in a straight line with constant acceleration).

*There are certain formulae used in constant acceleration problems.

Question 25

NOTE

Answer 25

Displacement (and speed) decreases as (you know what I mean) an object goes upwards (and vice versa as it falls downwards).

Gravity - a vector? - acts the same on everything, so when there’s no air resistance, everything falls at [virtually?] the same rate (earth is very large; makes little to no difference?).

Initial velocity is 0 if an object starts at rest/is dropped.

If it’s a free fall motion, the acceleration will be -9.8 m/s squared.

Question 26

What is a free-falling object?

Answer 26

An object whose velocity is falling under the sole influence of gravity. Does not encounter air resistance (same with an object falling in a vacuum). Acceleration is -9.8 m/s squared (this acceleration is known as acceleration due to gravity).

NOTE:

• Time between two positions is the same
• Displacement increases sharply
• Velocity increases proportionally
• Acceleration is constant throughout