Module 2 Foundations of Physics

Question 1

what are the seven SI units? what are the base units and what is the unit symbol for each one?

Answer 1

Question 2

what are the prefix symbol and the factor for peta, tera, giga, mega, kilo, deci, centi, milli, micro, nano, pico, femto

Answer 2

Question 3

answer these questions on si units and prefixes

Answer 3

Question 4

what are the unit names, unit symbol and units expressed in SI units for;

Force, Pressure, Energy/work done, pwower, electric potential difference, electric charge, frequency

Answer 4

Question 5

how do you convert degree celsius to kelvin?

Answer 5

add 273 e.g 20 degree celcius is 293 K

Question 6

answer these questions on derived units

Answer 6

Question 7

what is a systematic error?(imcluding zero errors)

what may they be caused by?

what do they affect?

Answer 7

• they are the same every time you repeat the experiment (they shift all values my the smae amount
• they may be caused by the equipment you’re using or how its set up e.g not lining the ruler correctly when meauring the extention of the spring
• thy affect the accuracy of your results

Question 8

what is a random error? give examples, and how you can reduce random errors

Answer 8

• they’re what makes the results a bit different each time you repeat an experiment.
• e.g if you measured length of a wire 20 times the chances are youd get a slightly different value each time due to your head being in a slightly different position when reading the scale OR you cant keep the controlled varibles exactly the same in each experiment
• use more sensitive apparatus so that youre results can be more precise OR repeating the measurements

Question 9

In a experiment how could you make your results more accurate?

Answer 9

• increase the number of your repeats which could help reduce the effect of the random errors in your results
• use the most appropriate equipment ( swapping millimetre ruler for a micrometer to measure the diameter of a wire) reducing the random error
• use a computer to collect data- using light gates to measure time interval rather than a stopwatch. makes results more precise by reducing human error.

Question 10

what is the difference between precise, accurate and reliable results?

Answer 10

precise= the variation you see when you measure the same part repeatedly with the same device

accuracy= difference between the measurements and the part’s actual value

reliable= when you repeat your results or compare them to somebody else and see that you get the same result

Question 11

what is the the absolute uncertainty?

how do you work out the absolute uncertainty?

Answer 11

-the total uncertainty for a measurement

absolute uncertainty= (max reading - min reading)/ 2

Question 12

what is the percentage uncertainty?

how do you work out the percentage uncertainty?

Answer 12

• the uncertainty given as a percentage of the measurement
• you divide the absolute uncertainty by the known measurement and the multiply by 100
  e. g (± 0.4/ 5) x 100= 8%

Question 13

what is the smallest uncertainty you can have in a measurement?

Answer 13

± half of one division on the measuring instrument used

Question 14

what is the rule when multiplying percentage uncertainties? e.g y=ab

Answer 14

you add the percentage uncertainties e.g

% uncern in y= % uncern in a + % uncern in b

Question 15

what is the uncertainty on a mean of repeated results equal to?

Answer 15

half the range of the results

e.g 0.5 A, 0.3 A, 0.3 A, 0.3 A

range= 0.5 - 0.3

range= 0.2

absolute uncertainty of mean= ± 0.1

Question 16

-what is the rule when dividing percentage uncertainties? e.g y=a/b

Answer 16

you add the percentage uncertainties e.g

% uncern in y= % uncern in a + % uncern in b

Question 17

what is the rule when squaring or cubing percentage uncertainties?

e.g y=a²

Answer 17

you multiply the uncertainty

e.g % uncern in y= 2 x % uncern in a

Question 18

how do you find the percentage difference?

Answer 18

-percentage difference= [first value- second value)/ (first value + second value)/2] x 100

Question 19

what is a scalar quantity

Answer 19

a qauntity that has magnitude (size) but no direction

Question 20

give examples of scalar quanities

Answer 20

• energy
• power
• mass
• voltage
• electric charge
• density
• work done
• denisty
• volume
• frequency
• electrical resistance

Question 21

answer these questions on scalars and vectors

Answer 21

Question 22

what is a vector quantity?

Answer 22

a quantity that has both magnitude and direction

Question 23

give examples of vector quanities

Answer 23

weight

force

momentum

friction

field strength

Question 24

where two vectors are parallel, you just add them together to fnd the resultant vector. the direction of the reultant is the same as the individual vectors but its magnitude is __________

where two vectors are antiparallel you call one direction positive (arrow head to the left) and the other negative (arrow head to the right), so you add the vectors to find the resultant.

Answer 24

where two vectors are parallel, you just add them together to fnd the resultant vector. the direction of the reultant is the same as the individual vectors but its magnitude is greater

Question 25

Answer 25

resultant=- -3.0 + 4.0 = +1.0 (towards the right)

Question 26

there are 2 methods of drawing perpendicular vectors

Answer 26

1. Calculation: calculation using pythagoras theorem to find the magnitude of the resultant vector and trigonometry to find magnitude
2. Scale Drawing: using sharp pencils, a long rule and protractor

Question 27

answer these questions on parallel, antiparallel and perpendicular vectors

Answer 27

Question 28

what are the two equations for the two components when resolving a vector

Answer 28

Fx=Fcos(angle)

Fy=Fsin(angle)

Question 29

work out this question

Answer 29

Question 30

answer this question

Answer 30

Question 31

answer these questions

Answer 31

Question 32

how do you add non perpendicular vectors?

Answer 32

1. drawing by scale diagram: you will need to do this when both the magnitude and resultant are unkown. You can use a protractor to work out the angle in between the know forces (usually the opposite of the resultantforce you want to work out) and a ruler to measure the resultant force, mention the angle and which force it is relative to
2. calculations using cosine and sine: the angle between the know forces is minus the given angle from 180 so then you can work out the resultant force using the cosine rule (a² = b² + c² - 2bc cos(angle)). To find the angle you use the sine rule (a/sin A= b/sin B)
3. vector resolution: for this method the diagram shown or you have drawn will be the same. you will be working out the vertidal and horizontal components. when working out the horizontal component you add the horizontal force to the diagonal force x cos(angle). once you have the forces for x and y you create another triangle putting x and y on the right sides. Then you work ou the resultant force by doing pythagoras theorem. to work out the magnitude you use tan-1.

Question 33

Two forces of 5.0N and 3.0N act on a single point at 60 degrees to each other. What is the magnitude and the direction of the resultant force?

Answer 33

Question 34

how do you subtract vectors?

Answer 34

Question 35

answer these summary questions on adding non perpendicular vectors

Answer 35

answers