what were the dependant and independent variables in the pendulum swing experiment and what were their units?
dependant variable: period of the pendulums oscillation, measured in seconds
Independant variable: length of the pendulum, measured in metres
how does the acceleration of an object experienced on earth change when its mass changes?
nothing happens, because the acceleration due to gravity on the earths surface is the same for any mass
newton showed this by rolling highly polished balls off polished ramps, and noticing different sized objects fall down the ramp at the same rate
is the acceleration due to gravity a constant on earth?
no
why isnt g a constant?
because it can vary with:
- geographical density of the surrounding environment. places where the lithosphere is thick(mountain ranges/mineral deposits) experience greater gravitational force compared to places of less dense rock or water
- an objects altitude above the earth. high altitudes experience less gravitational force toward the earth
- location on the surface of the earth as at the equator the globe bulges outwards due to the earths rotation
how do you increase reliablity in this experiment?
repeat each text a minimum of 2-3 times for each length and then collect an average for each length
you may also compare results with others in the classroom
how do you maintain the validity of an experiment?
- you must keep all variables constant
- you must use the correct equipment for the experimental investigation you are currently undertaking, you would not use a stopwatch to measure the length of a pendulum
how would you assess the accuracy of the data collected?
i would compare my result for g with the value of g at my location using some credible and reliable secondary source such as the national measurement institute. if my value of g is close to the recorded value, my results are accurate
what is the formula for T in the pendulum experiment?
T = 2π√(L/g)
what was performed in the method to improve the accuracy of the results gathered?
- the time taken for 10 oscillations was recorded over just one oscillation. this spreads the error in inherent in starting and stopping the stopwatch over a larger time.
- a stopwatch was used to record the time for 10 oscillations to 3 decimal places
why does the angle in the pendulum experiment have to be relatively small?
it must be less than 15 degrees to ensure the pendulum experiences a form of simple harmonic motion in which the equation to calculate g can be used accurately
what assumptions are made in the experiment?
- the string is massless
- the string is inextensible(does not change in length)
- the string is always taut(always tension in the string)
- there is no friction of air resistance
- -motion of the pendulum remains in two dimensions (traces out an arc rather than an elipse)
what are the controlled variables in this investigation?
- mass of bob
- initial angular displacement from vertical
- equipment used
- initial pendulum velocity
what should graphs have!!!!?
- TITLE
- AXIS WITH UNITS
- LINE OF BEST FIT
- GRAPH SHOULD BE BIG
- TRIANGLE TO CALCULATE GRADIENT MUST BE BIG AND MUST CONNECT TO POINTS IN DATA
how can you assess the reliability of the data collected?
- establish a mean value of the period for each length, and observe the difference between the measured value and the average when repeated. if the difference is substantial, then the experiment is not reliable.
- the data collected can also be compared with other results in the class. if the results when compared highlight similarities, then the results are fairly reliable
what materials were needed to perform this investigation?
- retort stand
- 50g mass
- string
- bosshead and clamp
- ruler
- protractor
- stopwatch or computer based technology
how to improve (1) and assess accuracy (2) of the pendulum prac?
(1) measure the time taken for an integer number of oscillations which is more than that of 10, say 20, then divide value by 20 to achieve time for one oscillation
also can use computer based technologies such as a data logger which will alleviate chances of systematic error
(2) compare the calculated value of g with literature value of g at the location where the prac is taking place recorded in a reliable and credible source
in any prac especially the pendulul one, how should you draw a line of best fit?
equal number of data points above and below the line while also going through a minimum of two data points
what were the materials needed for the distinguising of intertial and non-intertial reference frames prac?
- retort stand
- bosshead and clamp
- weight
- string
- trolley
- 50g mass
method for the reference frames prac?
1) set up the apparatus as shown
2) subject the apparatus to the following five situations and describe how the accelerometer (ball) behaved
- accelerating from rest
- stationary
- constant velocity
- decelerating
- turning around a bend
what were some of einsteins throught experiements?
- looking in a mirror on a train that is moving at the speed of light, will i see my reflection???
- relativity of silumtaneity, two lighting bolts strike simultaenously in an observers frame of reference, while one strikes before the other in a moving trains frame which is moving near the speed of light
- a construction worker ontop of a building will fall and feel weightless blah blah blah…..
