Experiment 4 Static
Topic: Statics
Title: Density of an object
Objectives: To determine the density of an object using a spring system.
Theory:
 |
| Figure 2. h must be constant |
Figure E7- 2
Figure 2 shows forces acting at point Q where T the tension in the thread is,F
is the tension in the spring and W is the weight of object A.
is the tension in the spring and W is the weight of object A.
The equation below show the condition for equilibrium at point Q
Tsin =F,
T cos =W,
Hence,
w=F tan ……………(1)
From Figure 1,we have
tan =xh
For the spring,
F=k(l-l0),
Where kare the spring constant and l0 the unstretched length.
From equation (1),
W=k(l-l0)xh,
l=wkhx+l0 .
For constanth, the gradient s of graph l against x is proportional to W .
The weight of object A,
W=VAg……..(2)
Where V are the volume and A the density of object A.
When object A is immersed in water, the up thrust acting on the object is given by
Up thrust=W-W'=VWg………(3)
Where W' is the apparent weight of object A and Wthe density of water.
Dividing equation (2) by equation (3),
(3)(2)WW-W'=AW,
A=ss-s'w……….(4)
Where s' is the gradient of graph l'against x'.
Apparatus:
ii. Thread
iii. A pendulum bob
iv. An object A
v. A half-metre ruler
vi. Two retort stands with clamps
vii. Weights to stabilise stands
viii. A 500 cm3 beaker
Procedure:
(a) Set-up the apparatus as shown in Figure 3. (Note: make sure that the spring is
stretched such that it is just enough to be in horizontal position).
stretched such that it is just enough to be in horizontal position).
(b) Make a reference mark P on the thread which hangs the pendulum bob. This mark
should be higher than the level where object A is tied to the spring.
should be higher than the level where object A is tied to the spring.
(c) Move the retort stand on the left to increase the angle B and adjust the loop until the
spring is horizontal.
spring is horizontal.
(d) Measure and record the corresponding length of the spring L and horizontal distance
from P to the thread x.
from P to the thread x.
(e) Repeat step (c) for different values of L and x.
(f) Plot a graph of L against x.
(g) Repeat step (c) to (e) with object A immersed in a beaker of water.
(h) Measure and record the corresponding L’ and x', using the same range of x in step (e).
(i) On the same axes as in step (f), plot a graph of L’ against x'.
(i) Determine the gradients s and s'.
(k) Determine the density of the object A.
Data:
Graph:
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