A Level Physics Notes: Experimental Physics – The Bending of a Beam
Apparatus:
Two metre rulers (one thinner than the other), 1kg load, string, two pivots, two wooden blocks for the pivots, set square.
Diagram:
Procedure:
1. Set up the apparatus as shown in the diagram above. The thinner
metre ruler should be placed so that the pivots lie below the 100 and
900mm marks. The 1kg mass should hang from the 500mm point. This will
mean that the length of the ruler,
between
the pivots is 0.800m
2. Use the other metre metre to measure the sag,
of
the thinner metre ruler caused by the 1kg mass. You should attempt to
do this more than once.
3. Repeat the above for five more values ofbetween
0.500m and 0.900m. In all cases the 1kg mass should hang from the
mid-point between the pivots.
4. For each value of L calculate:
(a)
&
(b)
5. Draw a graph ofagainst
6. From this graph, using the theory shown below, confirm, or
otherwise, that the relationship between the sag,and
the beam length,is
given by
7. Explain how you measured the sag,of
the ruler.
Theory:
Let
Taking logs on both sides gives
which can be rearranged into
This equation has the form of a straight line, that is
In this case the
term
corresponds to
and
the
term
to
The
gradient of your graph will be n so you can find the value of
in
the relationship