Save
Paper 3
10. Practical Skills
RP03 - Determination of g
Save
Share
Learn
Content
Leaderboard
Learn
Created by
Study_Potato
Visit profile
Cards (16)
What is 'g'?
The
Gravitational Field Strength
What is meant by 'free-fall'?
An object is said to be in
free-fall
if the only force acting on it is
gravity
This means that any
resistive
forces that are acting can be considered to be
negligible
What graph can be plotted from experimental data to determine 'g'?
A graph of
2h/t against
t can be
plotted
The
value
of 'g' is
equal
to the
gradient
of the
line plotted
Describe how an electromagnet system can be used to determine 'g'
A
magnetic ball bearing
can be released by an
electromagnet clamped
at a known
height
The
timing system
starts when the electromagnet is switched
off
and the timer is
stopped
when the ball lands on the
finish pad
When using a clamp stand in this experiment, what safety precaution should be taken?
The clamp stand should have a
counterweight
or a
G-clamp
attached to its
base
to provide a moment to
prevent
the clamp
stand from toppling over
What safety precaution should be taken when using an electromagnet?
Electromagnets
heat up
over time
To reduce this
heating effect
, you should
switch
it
off
when not in use
Suggest how light-gates could be positioned to ensure that the ball falls directly through them
A
plumb
line could be used to demonstrate the
expected
path of the ball
This allows the
light-gates
to be
positioned
in appropriate places so that the ball will
fall
through them
Why is it better to use a small ball bearing over a larger ball?
The smaller the ball, the
smaller
the effects of
air resistance
In the case of a small ball bearing, these effects can be considered to be
negligible
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 quick enough
Explain why this experiment would not be valid if the air resistance acting on the ball wasn't negligible
The ball wouldn't be in
free fall
since the
acceleration
would not be purely due to the force of
gravity
The acceleration would also be
variable
since
air resistance
increases with
speed
, and so the
uniform acceleration equations
couldn't be used
Suggest why your obtained value of 'g' may not be the same as the accepted value
Delays
in the
timing equipment
(if using a stop clock, this will be human reaction time)
Resistive forces
may be significant
Errors
in
height measurements
, such as measuring from different positions on the ball each time
Would you expect your value of 'g' to be greater or lower than the accepted value?
You will most likely obtain a value that is
lower
than the accepted value
due to
air
resistance
reducing
the
downwards resultant force
acting on the object
How could your results be improved?
You should take
repeated readings
at each
height
and then calculate the
mean time taken
You should also ensure that
height measurements
are taken from the
same position
on the ball each time
What is the advantage of using light gates over a stop clock in this experiment?
Using light gates should result in a
lower uncertainty
in your
time measurements
A stop clock will involve human
reaction times
and therefore an
associated error
What is the minimum number of repeated readings you should take in this experiment?
You should take at least
3 repeat
readings at each
height
This allows for
anomalous
results to be more easily
identified
gradient derivation:
s = ut + 1/2 at^2
2s = 2ut + at^2
2s/t = 2u + at
where:
2s/t = y
2u = c
t = x
a = m