core practial 1 (a) Flashcards
what is the procedure for core practical 1 (a)
- drop a sphere from rest and record the time taken for it to fall through the trap door
- repeat step one twice more and find the average for t
- measure and record the height of the fallen object
- vary the height and repeat the steps 1-3 you should take the reading at least 6 different times
- use half the range in your readings for t as the uncertainty in t (calculate the uncertainty of t )
what are the equipment used for core practical 1 (a)
1- meter rule or a tape measure with millimeter resolution 2 - steel sphere 3 - electronic timer 4 - electromagnet to retain steel sphere 5 - trap door switch 6 - clap and stand 7 - low voltage power supply
how do we calculate the percentage uncertainty
range/average tine x 100%
how do you calculate the error bars
mt^2 and m/t^2
what is meant by free-fall
an object is said to be falling in free fall if the only force acting on it is its own weight under gravity, this means negligible forces are acting
what is meant by ‘g’
the gravitational field strength
why can the SUVAT equations be used in this experiment?
because the object would be failing in uniform acceleration. this is because the force of gravity is approximately constant to the earth’s surface
when plotting a graph of t^2 against h, how is ‘g’ determined
the gradient of the graph would be t^2/h the acceleration “g” would equal 2/gradeint. this would come from the SUVAT equation of s= ut +1/2at^2 where u=0 a=g s=h
when plotting a graph of v^2 against h, how is “g” determined
the gradient would be v^2/h. making the acceleration “g” equal to half the gradient this would come from the SUVAT equation of v^2 = u^2 + 2as where u= 0 a=g s=h
When using a clamp stand in this experiment, what safety precautions should be taken
the clamp would have a counterweight or a G-clamp attached to its base to provide a moment to prevent it from topping over
suggest how light-gates could be positioned to ensure that the ball or dowel falls directly through them
a plump line could be used to demonstrate the expected path of the object, this would allow us to place the light gate in the appropriate places so that the ball would fall through it
why is it advantageous to use a small ball-bearing over a large ball
the effects of air resistance are less effective on the small ball-bearing, therefore our assumption that air resistance forces are negligible is more valid if a small-bearing ball is used
why should there be a gap between the release position and the first light-gate?
there should be a gap to ensure that the time over which the ball is passing through the light gate is negligible (the ball is moving sufficiently quickly at the light gate)
explain why this experiment would not be valid if the air resistance acting on the ball wasn’t negligible
the object would be in free fall since acceleration wouldn’t be purely due to the force of gravity also, the acceleration would be variable since air resistance increases with speed, so the uniform acceleration equations couldn’t be used
suggest why your obtained value of “g” may not be accepted value
- delays in time equipment (like a human error when using stopwatches)
- resistive forces are acting
- errors of height measurement (measuring from different positioning on the ball each time)
what are the advantages of using light-gates over a stop-clock in this experiment
using light gates would lower uncertainty in your time measurements while using stop-clock allows human error (because of human reaction times) which should increase the uncertainty in your time accuracy
how could your results be improved
- by taking repeat readings at each height then calculating the meantime taken from all non-anomaly results
2, by making sure the height measurement is taken at the same point on the ball every time
how should you calculate the uncertainty in your time readings
the uncertainty in time can be considered to equal half the range of your time readings, measured for each height
how to determine the percentage uncertainty in t^2
to calculate the percentage value of any squared variable you just double it
when plotting a graph how should you determine the scales for the axes
the scale should be chosen so that the graph fills at least half the space. and we should pick numbers that can be easily split into the squares of the page
what is the minimum number of repeat readings you should take in this experiment
you should take a minimum of 3 so that anomaly would be identified easily
what is the equation used to convert uncertainty into a percentage uncertainty (%U)
(uncertainty/mean value) x 100
how can the percentage difference (%D) between your value “g” and the accepted value be calculated
{(k-g)/g} x 100%
would you expect your value “g” to be greater or lower than your accepted value
you would obtain a value lower than your accepted value that is because air resistance is acting against the downward resultant force acting on an object
