core practial 1 (a)

Question 1

what is the procedure for core practical 1 (a)

Answer 1

1. drop a sphere from rest and record the time taken for it to fall through the trap door
2. repeat step one twice more and find the average for t
3. measure and record the height of the fallen object
4. vary the height and repeat the steps 1-3 you should take the reading at least 6 different times
5. use half the range in your readings for t as the uncertainty in t (calculate the uncertainty of t )

Question 2

what are the equipment used for core practical 1 (a)

Answer 2

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

Question 3

how do we calculate the percentage uncertainty

Answer 3

range/average tine x 100%

Question 4

how do you calculate the error bars

Answer 4

mt^2 and m/t^2

Question 5

what is meant by free-fall

Answer 5

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

Question 6

what is meant by ‘g’

Answer 6

the gravitational field strength

Question 7

why can the SUVAT equations be used in this experiment?

Answer 7

because the object would be failing in uniform acceleration. this is because the force of gravity is approximately constant to the earth’s surface

Question 8

when plotting a graph of t^2 against h, how is ‘g’ determined

Answer 8

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

Question 9

when plotting a graph of v^2 against h, how is “g” determined

Answer 9

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

Question 10

When using a clamp stand in this experiment, what safety precautions should be taken

Answer 10

the clamp would have a counterweight or a G-clamp attached to its base to provide a moment to prevent it from topping over

Question 11

suggest how light-gates could be positioned to ensure that the ball or dowel falls directly through them

Answer 11

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

Question 12

why is it advantageous to use a small ball-bearing over a large ball

Answer 12

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

Question 13

why should there be a gap between the release position and the first light-gate?

Answer 13

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)

Question 14

explain why this experiment would not be valid if the air resistance acting on the ball wasn’t negligible

Answer 14

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

Question 15

suggest why your obtained value of “g” may not be accepted value

Answer 15

1. delays in time equipment (like a human error when using stopwatches)
2. resistive forces are acting
3. errors of height measurement (measuring from different positioning on the ball each time)

Question 16

what are the advantages of using light-gates over a stop-clock in this experiment

Answer 16

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

Question 17

how could your results be improved

Answer 17

1. 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

Question 18

how should you calculate the uncertainty in your time readings

Answer 18

the uncertainty in time can be considered to equal half the range of your time readings, measured for each height

Question 19

how to determine the percentage uncertainty in t^2

Answer 19

to calculate the percentage value of any squared variable you just double it

Question 20

when plotting a graph how should you determine the scales for the axes

Answer 20

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

Question 21

what is the minimum number of repeat readings you should take in this experiment

Answer 21

you should take a minimum of 3 so that anomaly would be identified easily

Question 22

what is the equation used to convert uncertainty into a percentage uncertainty (%U)

Answer 22

(uncertainty/mean value) x 100

Question 23

how can the percentage difference (%D) between your value “g” and the accepted value be calculated

Answer 23

{(k-g)/g} x 100%

Question 24

would you expect your value “g” to be greater or lower than your accepted value

Answer 24

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