Ch 1 Physical Quantities and Units Flashcards
All physical quantities consist of __________ and ___________.
magnitude and unit
What are the 5 base quantities?
mass, length, time, current, temperature
What is the SI unit of mass?
kilogram (kg)
What is the SI unit of length?
meter (m)
What is the SI unit of time?
second (s)
What is the SI unit of current?
ampere (A)
What is the SI unit of temperature?
kelvin (K)
What is the SI unit of speed?
meters per second (m/s)
What is the SI unit of acceleration?
meters per square second (m/s2)
What is the SI unit of density?
kilogram per cubic meter (kg/m3)
What is a scalar quantity?
A quantity with only magnitude.
What is a vector quantity?
A quantity with both magnitude and direction.
Convert 0.001 m to mm.
1 mm
Convert 300 g to kg.
0.3 kg
Convert 0.00001 m to micrometer.
10 micrometer
Convert 200 000 W to MW.
0.2 MW
Convert 20 000 000 J to GJ.
0.02 GJ
Give one example of a vector quantity.
Any of the following is correct: velocity, acceleration, force, displacement, weight.
Give one example of a scalar quantity.
Any of the following is correct: speed, distance, time, mass, current, voltage, resistance etc.
Newton’s third law involves two quantities which are equal in size and opposite in direction. What is the unit for these two quantities?
N
Which quantity is a scalar?
A acceleration
B force
C temperature
D velocity
C Temperature
Vectors can be represented using arrows:
The direction of the arrow shows _____________
The length of the arrow represents ____________
Direction,magnitude
Rulers can be used to measure small distances of a few cm. They are able to measure to the nearest
mm
When measuring larger distances (of a few metres) a ___________ is more appropriate or, when measuring even larger distances, ___________
tape measure,Trundle wheel
a. Measuring cylinders can be used to measure the ________ of liquids
b. The change in volume of the liquid in the cyclinder is equal to ______________.
a. Volume
b. Volume of irregular shaped object
When reading the volume of the scale of measuring cyclinder, use the __________ meniscus
Lower/bottom
Suppose you have to measure the thickness of a sheet of paper. The thing that you are trying to measure is so small that it would be very difficult to get an ________ answer
If, however, you measure the thickness of 100 sheets of paper you can do so much more accurately. Dividing your answer by 100 will then give an accurate figure for the thickness of one sheet
accurate
This process of taking a reading of a large number of values and then dividing by the number, is a good way of getting accurate values for small figures.
Think of another example where we might use this technique.
the time period of a pendulum – measure the time taken for 10 (or more) swings and then divide that time by no. of swings
Accuracy
a measure of how close the results of an experiment agree with the true value.
The accuracy of a reading can be improved by _______________________
repeating the measurements.
Precision
is a measure of how close the results of an experiment agree with each other. It is a measure of how reproducible the results are.
is how close the measured values are to each other but they may not necessarily cluster about the true value.
High precision implies
a small uncertainty and small random error.
When there is high accuracy
there will be small systematic error
For accurate measurement, the eye must always be placed vertically above the mark being read. This is to avoid _________ which will give rise to inaccurate measurement.
Parallex error
Parallax errors affects the accuracy of the measurement.
- If you consistently used the incorrect angle to view the markings, your measurements will be displaced from the true values by the same amount. This is called __________.
- However, if you used different angles to view the markings, your measurements will be displaced from the true values by different amounts. This is called ___________ .
- systematic error
- random error
Reading the tape from ticker tape timer
For X, the dots are evenly spaced. Since the length is 1 m, the spacing between each dots is 0.2 m. We can calculate the speed of the object using Speed=DistanceTime=0.20.1=2m/sSpeed=DistanceTime=0.20.1=2m/s Hence, X represent the tape from an object that is moving at constant speed.
For Y, the spacing between the dots increases as time passes. Since the dots are made with a fixed time interval, the time in the formula above is fixed. We will get an increasing speed as the distance between the dots increases. Hence, Y represent the tape from an object that is accelerating.
For Z, the spacing between the dots decreases as time passes. Using the same reasoning as above, Z represent the tape from an object that is decelerating.
1 cm = 0.01 metre
1 kg = ___________ grams
1 GB = 1 000 000 000 bytes
0.000 0052 s = _________s
1000, 5.2×10−6
