Physics Labs
1
Table of Contents
Hooke’s Law…………………………………………………….………..3
Conservation of Momentum………………...………………….…………5
Personal Power……………………………………………………………6
I-V Relationships……………………………………………………….....7
Potential Difference in Series……………………………………………..9
Current in Parallel…………………………………………………………10
PD Prompts…………………………………………………………….….13
PD number 1…………………………………………………………...….15
PD number 2………………………………………………………………16
Relationship between Mass and Volume of Objects……………………...17
Relationship between Mass and Weight…………………………………..21
The Pendulum…………………………………………………………......26
Centre of Gravity for Lamina………………………………………..……30
Reflection of Light………………………………………………………..32
Measuring Area……...……………………………………………………34
Analogous System……………………………………………………...…37
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HOOKE’S LAW (Skill: ORR, AI)
Objective
To determine if a body (spring) obeys Hooke’s law
Apparatus
Meter rule, spring, holder, slotted masses, pointer, (plasticine or masking tape/optical
pin), two retort stands, set square.
Diagram
Procedure
The apparatus was set up as shown in the diagram. The meter rule was vertical and the pointer
was at a right angle to the spring and horizontal. The zero side of the rule was at the top and the
pointer moved directly over the scale. The holder was placed onto the spring and the reading was
recorded, the position of the pointer, on the meter rule without any slotted masses. Masses, m,
were added continually and the pointer position was recorded each time. 8 readings were
obtained for l. The masses were removed in the same order and the pointer position was rechecked.
Data Collected
Record l0.
Tabulate results for
m – mass added in grams
F – weight added in Newton
l1 – pointer position loading
l2 – pointer position unloading
e – extension
3
Data Analysis
1. Plot a graph of F (y-axis) against e (x-axis)
2. Find the gradient of the graph.
3. What force produces an extension of 1.3 cm?
4. Is F proportional to e? Justify your answer.
5. Does your system obey Hooke’s law?
-
Yes, the system does obey Hooke’s Law.
6. What would one expect to see in l1 and l2 if the spring had a permanent set?
-
One would expect that no extension would be produced if the spring has a permanent set.
7. Has the elastic limit been exceeded?
-
No, the elastic limit has not been exceeded. If the spring was exceeded to its limit, then, it
would have to be stretched beyond the limit of proportionality. When the spring is
stretched it would not return to its original size when there is no force acting upon it.
8. Identify two precautions you took in order to get good readings.
a. When measuring the masses, do not move it.
b. Ensure that the measuring starts at the body of the spring.
Conclusion
-
Hooke’s Law was obeyed because the body was directly proportional when force was
acted upon it.
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CONSERVATION OF MOMENTUM (Skill: AI)
Objective
To determine the principle of conservation of momentum
Apparatus
Four identical balls on a support.
Diagram
Procedure
The first ball was pulled aside, released and the observation was recorded.
Data collected
Record your observation in a suitable format.
Data analysis
1. What happens to the momentum of the first ball?
-
The energy from the first ball is transferred to the second ball.
2. What happens to the momentum gained by the second ball?
-
The energy from the second ball is transferred to the third ball.
3. By substituting into the formula for momentum conservation, show how you
Observations are supported by the principle.
4. Describe what has occurred in terms of forces.
5. Describe the basic energy changes taking place in the system
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PERSONAL POWER (Skill: AI)
Objective
To find out the magnitude of your personal power.
Apparatus
Steps, ruler, scale, stop clock.
Procedure
The scale was used to find the mass, m. The ruler was used to find the average height, h, of one
step. The number of steps in a flight of stairs was checked and the total vertical height involved
was determined. The clock started while simultaneously running up the stairs. The clock was
stopped upon arrival at the top of the stairs. The procedure was repeated in order to obtain two
more values for the time, t, taken to climb the stairs. The procedure was repeated at different
rates – walking, jogging, running.
Data collected
Record your data in a suitable format.
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Data analysis
1. What units must m, g, h and t be in if we want to calculate power in standard
units?
-
“m” must be in the unit kg, “g” must be in the unit m/s^2, “h” must be in the unit m and
“t” should be in the unit s.
2. Calculate your power in each case in standard units.
3. Convert your answers to kilowatts.
4. Is the same amount of work done in walking and running up the stairs?
-
Yes, the same amount of work was done because it was the same distance for both cases.
5. Is the rate of doing work the same in both cases?
-
No, the rates are different because there were different speeds.
I-V RELATIONSHIPS (Skill: AI, ORR)
Objective
To compare the characteristics (I/V graphs) for
(a) a metallic conductor
(b) the semi-conductor diode.
(c) a solution of copper sulphate in water using copper electrodes.
Apparatus
Metallic conductor (resistor), diode, copper sulphate solution, voltmeter, ammeter,
rheostat, battery, connecting wires.
Diagram
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Procedure
The equipment was set up as shown in the diagram with the component at X and with rheostat at
maximum. The readings of current were recorded, I, on the ammeter and voltage, V, on the
voltmeter. Pairs of values of current and voltage were obtained by removing the rheostat and it
was ensured that the values are spread out over the entire range. The direction of the component
was reversed and the procedure was repeated and all current and voltage values were recorded as
negative (the circuit ran with one battery to obtain a lower range of current and voltage)
Data analysis
1. Draw a graph of current against voltage for the component(s) you have taken
readings for (include positive and negative values on the same graph).
2. Sketch the characteristics for all three components.
3. For which component(s) does changing the direction not affect the voltage
and current readings?
4. From your characteristics, what is special about the semiconductor diode?
-
A diode is a two-terminal semiconductor electronic element that exhibits nonlinear
current-voltage characteristics. It allows current in one direction at which its resistance is
very low during forward bias.
5. What is the meaning of the gradient?
-
the rate of change with respect to distance of a variable quantity, as temperature or
pressure, in the direction of maximum change.
6. Which component(s) show(s) as current increases (a) the gradient
increases (b) the gradient decreases (c) gradient is constant.
7. Which component shows as current increases (a) the resistance increases (b)
The resistance decreases. State how you deduced your answer.
8. Is the formula V = IR valid for all three components?
-
Yes it is
9. What special name is given to devices whose resistance remains constant
as current increases?
8
-
An Ohmic device
POTENTIAL DIFFERENCE IN SERIES (Skill: AI)
Objective
To investigate potential differences in series circuits.
Apparatus
Battery, ammeter, voltmeter, three resistors of different magnitudes, rheostat, switch,
connecting wires.
Diagram
Procedure
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The apparatus was set up as shown in the diagram with the voltmeter in position A, and the
rheostat at maximum and the switch off. The teacher was asked to check the circuit. The switch
was inserted and the rheostat was adjusted until a large voltage was obtained and the range of the
voltmeter was not exceeded. The voltage, V, was recorded in the position A. The rheostat was
not adjusted further. The voltmeter readings in position B, C and D were recorded in turn. For
positions B, C and D, the corresponding values of the resistors whose potential difference were
measured was recorded.
Data collected
Data analysis
1. Across which resistor is the potential difference the greatest?
2. Find the sum of the potential difference across the three resistors. What do
you notice about his sum?
3. What can you deduce about the voltage across components in a series circuit?
4. Using V= IR calculate the current flowing through each resistor.
CURRENT IN PARALLEL (Skill: AI)
Objective
To investigate current in a parallel circuit
Apparatus
Battery, ammeter, voltmeter, three resistors of different magnitudes, rheostat, switch,
connecting wires.
Diagram
Procedure
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The circuit diagram above was set up with ammeter A and the rheostat at maximum. The teacher
was allowed to check the circuit. The switch was closed and the rheostat was adjusted so that a
large current is flowing but it did not exceed the range of the ammeter. The reading was recorded
on the ammeter at his position A. The position of the ammeter was changed to B, C, D and E and
the current reading at each position was recorded. The corresponding values of the resistors in
branches B, C, and D were also recorded.
Data collected
Position
Current/A
Resistance/ Ω
A
1.65
-
B
0.80
10
C
0.4
20
D
0.20
40
Data analysis
1. In which branch B, C or D is the current flowing the largest? Why is this so?
-
B. It would be B because the resistance is low, so it is affecting the flow.
2. What is the value of the current entering junction 1?
-
The value of current entering junction 1 is 1.65A
3. What is the sum of the currents leaving junction 1?
-
The value of current leaving junction 1 is 1.65A
4. What is the sum of the currents entering junction 2?
-
The value of current entering junction 2 is 1.65A
5. What is the value of the current leaving junction 2?
-
The value of current entering junction 2 is 1.65A
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6. What can you deduce about the current entering and leaving a junction?
-
The current entering and leaving is the same.
7. By using V = IR, calculate the voltage across each resistor in each branch.
-
branch B
V = 0.80 × 10
V = 8V
-
branch C
V = 0.4 × 20
V = 8V
-
branch D
V = 0.20 × 40
V = 8V
8. What can you deduce about the voltage across each branch in a parallel circuit?
-
The voltage is the same.
9. Why should the connections for domestic appliances be in parallel?
-
We should connect electrical appliances in parallel so that each appliance would get full
voltage. If one appliance is faulty, other appliances will continue working. Each
appliance will get the desired current according to their resistance.
Conclusion
It was concluded that the voltages are the same for every resistor.
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PHYSICS (PLANNING AND DESIGN)
INSTRUCTION: You are required to choose FOUR (4) problems from the following. Write a
proposal (planning and design) on EACH problem.
1. A student claims that the velocity of a bead is the same as it falls through different types
of liquid. Plan and design an experiment to verify this claim.
2. Plan and design an experiment to verify the following claims (a and b):
The spring constant doubles if two similar rubber bands are connected in series
The spring constant halves if two similar rubber bands are connected in parallel
3. In an experiment to investigate the period of a pendulum, paper clips can be linked in a
chain and swung as a simple pendulum. The period, T, of the pendulum depends on the
number of paper clips, n, of the paper clips used. A student suggests that the relation
between T and n is T=kn where k is a constant.
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4. Plan and design an experiment to test the hypothesis “sawdust is a better insulator than
Styrofoam”.
5. During the summer and the winter season the Eiffel Tower height is noticed to change.
Plan and design an experiment to validate the claim and what would be the cause.
6. Jane loves to drink Milo in the mornings, but he complains that it is taking too long to
cool. Her friend Penny suggested that he use a cup with a larger surface area so the Milo
will cool faster. Plan and design an experiment to test whether the surface area affects the
rate of cooling of a hot liquid.
7. Matthew is an electrician and thinks that if he uses long electrical wires for his work, he
will get higher resistance with current. Plan and design an experiment to check if the
length of the wire will have an effect on the value of the resistance.
8. Martin asked his father why he is able to float so easily in the sea water but has so much
difficulty floating in the swimming pool. His father replied that it has something to do
with the water and that he should investigate what it is. Martin asked his father “does it
have to do with density?” His father replied “maybe, but you can find out”.
9. You are given a 100g spring balance, rubber bungs, string, alcohol, tap water, sea water,
large beaker, stand and clamp, hydrometer. Plan and design an experiment that Martin
could conduct to determine the effect of density of liquid on a body that is in it.
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The PD’s
1. In an experiment to investigate the period of a pendulum, paper clips can be linked in a
chain and swung as a simple pendulum. The period, T, of the pendulum depends on the
number of paper clips, n, of the paper clips used. A student suggests that the relation
between T and n is T=kn where k is a constant.
Objective
To investigate the relationship between the period of a pendulum
Apparatus
Pendulum, ruler, stop clock/stopwatch, set square, retort stand, paperclips and a chain
Procedure
1. Set up the apparatus.
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2. Set the ruler into a vertical position.
3. Use a ruler to measure the exact length of the pendulum and place 5 paper clips on the
chain.
4. Set the oscillating pendulum with a small amplitude in place.
5. Start the countdown to find time (t) for 10 oscillations and repeat for (t2) to ensure
accuracy.
6. Change the pendulum and repeat the procedure.
7. Spread the readings over the entire range.
PD #2
Matthew is an electrician and thinks that if he uses long electrical wires for his work, he will get
higher resistance with current. Plan and design an experiment to check if the length of the wire
will have an effect on the value of the resistance.
Objective
To investigate if the length of a wire will affect the resistance
Apparatus
90cm of polycab wire, scissors, ruler, digital multimeter
Procedure
1. Gather your materials as stated above
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2. Cut the wire with scissors into two separate wires with the measurement 45cm each.
3. Measure each wire by putting probes on the edges of the wires, and measure them 6 times
each.
4. Record the resistance of the two wires.
RELATIONSHIP BETWEEN MASS AND VOLUME OF OBJECTS (Skill: ORR, AI)
Objective
To determine the relationship between the mass and volume of plastercine
Apparatus
Six sets of plastercine, triple beam balance, eureka can, measuring cylinder, beaker, thread,
water
Procedure
The mass of each plastercine was determined using the triple beam balance. Water was poured
into the eureka can until it began to overflow through the sprout into the beaker. The beaker was
removed and replaced with an empty measuring cylinder. The plastercine was tied to a piece of
string and was gently lowered into the can. The volume of water displaced into the cylinder was
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recorded. The experiment was repeated twice and the average volume of water displaced was
found. The procedure above was repeated for another set of plastercine.
Data collected
Record your data in a suitable table, showing VOLUME and MASS
Volume (cm^3)
Mass (g)
65
110.5
55
92.4
46
77.3
37
62.2
26
47.1
20
32.2
11
17.2
Data analysis
1. Do a table analysis to find out if mass is directly proportional to average volume
2. Plot a graph of mass against average volume
.
Find S, the gradient of the graph.
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19
0.
Which physical quantity does the gradient represent?
0.
Convert the gradient to S.I unit?
Conclusion
It was concluded that the mass is directly proportional to the average volume.
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RELATIONSHIP BETWEEN MASS AND WEIGHT (Skill: ORR, AI)
Objective
To investigate the relationship between mass and weight
Apparatus
Ten different sizes of plastercine, triple beam balance and spring balance.
Procedure
Ten different sizes of plastercine were obtained. The mass of each plastercine was measured
using the triple beam balance. The weight of each plastercine was measured using a spring
balance.
Data collected
Record your data in a suitable table, showing mass (grams) mass (kilograms) and weight
(Newtons).
Mass (kg) Weight (N) Grams (g)
0.01
0.1
10
0.04
0.4
40
0.05
0.5
50
0.06
0.6
60
0.09
0.9
90
0.13
1.3
130
0.21
2.1
210
Data analysis
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1. Do a table analysis to find out if mass is directly proportional to weight
2. Plot a graph of weight against mass, start graph from the origin (0,0). Make sure the line
passes through the origin.
22
23
1. Find g, the gradient of the graph.
2. Which physical quantity does the gradient represent? Gravity
3. Convert the gradient to S.I unit?
4. Write the equation for the graph
5. Using the equation above what would be the weight of a 250 kg mass on Earth
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6. If this experiment had been conducted on the Moon the mass would have still been the
same. However, the weight of the plastercines would have been different. How would
they have been different?
-
It would be different because of the difference in gravity between Earth and the Moon.
7. If this experiment had been conducted on the Moon what would have happened to the
gradient of the graph. Would it have been greater or less than if the experiment was
performed on Earth? Explain.
8. The acceleration due to gravity on the moon 1.62 N/kg Using the equation above
what would be the weight of a 250 kg mass on the Moon.
Conclusion
-
It was concluded that mass is directly proportional to weight.
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The Pendulum
Objective
To investigate the relationship between length and period of a pendulum
Apparatus
Pendulum, ruler, stop clock/stop watch, set square, retort stand
Diagram
Procedure
The apparatus was set as shown in the diagram with the length ( l ), of the pendulum at about
80cm. The ruler was set in a vertical position. The ruler and set square was used to measure the
exact length of the pendulum. The oscillating pendulum was set with a small amplitude in one
place. The countdown method and timing was used to form a mid – reference line and to find the
time ( t ), for 20 oscillations. The timing was repeated for (t2) to ensure accuracy. The length of
the pendulum was changed and the procedure was repeated. The length was varied between l =
10.0 cm and 80.0 cm. The readings were spread over the entire range.
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Data collected
Length ( l )
0.8 m
0.7 m
0.6 m
0.5 m
0.4 m
0.3 m
0.2 m
t (20 oscl)
37.26 s
34. 97 s
32.35 s
29.45 s
26. 81 s
22. 97 s
18.84 s
t (20 oscl)
38.20 s
34. 89 s
32. 33 s
29. 64 s
26. 50 s
22. 96 s
18. 74 s
2
t average
37.73 s
34.93 s
32.34 s
29.54 s
26.65 s
22.96 s
18.79 s
T( )
1.88 s
1.74 s
1.61 s
1.47 s
1.33 s
1.14 s
0.93 s
t/
20
T
3.53 s
3.02 s
2.59 s
2.16 s
1.76 s
1.29 s
0.86 s
2
Data Analysis
1. Plot a graph of T against l.
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0.
Plot a graph of T against l.
0.
Use your graph to find the period of a pendulum whose length is 35cm?
0.
Find S, the gradient of the graph.
0.
Given that, find g
0.
What can you conclude about the relationship between l and T ?
2
2
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The relationship between L and T was directly proportional. When L increased T also
increased.
2
0.
Write an equation connecting T and l.
0.
What are the factors that affect the period of a simple pendulum?
2
2
The factors that affect the period of a simple pendulum are length of pendulum and angle of
displacement.
Conclusion
The relationship between length and period was found. The relationship between length and
period was directly proportional, when length increased, period also increased.
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CENTER OF GRAVITY FOR A LAMINA
Objective
To find the center of gravity of an irregular shaped object using the plumb line method.
Apparatus
Lamina (irregular shaped object), retort stand, plumb line, nail or pin, cork.
Diagram
Procedure
It was ensured that the pivot was stable. A hole was placed close to the edge of a body and it was
suspended on the pivot. It was swinging freely. The plumb line on the lamina was suspended
when the lamina was in equilibrium; the position of the plumb line was recorded with a X. The X
was placed close to the edge. The position of the plumb line was drawn in with a sharp pencil.
Another hole was placed in the lamina and the procedure was repeated and the new position of
the plumb line was located. It was repeated again from another position.
Data analysis
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1. Why must the intersection of the three lines be the center of gravity?
●
0.
That’s where most of the weight is so it can balance
List the important precautions in this experiment.
●
●
●
Ensure that the sphere is central
Ensure that there is no wind
Ensure that lamina swings freely
0.
When the procedure is repeated a third time, how will this distinguish whether the
location of the c.g. is accurate or not?
●
The lines would split the circles and they would also meet in the middle.
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REFLECTION OF LIGHT
Objective
To investigate the relationship between the angle of incidence and the angle of reflection
Apparatus
Paper, tacks, four optical pins, optical board, mirror, mirror support (block), protractor, sharp
pencil
Diagram
Procedure
The paper was tacked onto the board and a mirror line was drawn close to the edge of the longer
edge of the paper. A protractor was used to draw in a normal in the middle of the mirror line. The
protractor was used to measure out lines at angles of incidence 15 , 30 up to 75 A mirror was
placed on the line so that the silvered edge is on the line that was drawn. Two pins were placed
on the first incident (15 ), one (A) close to the mirror and one (B) as close to the edge of the
paper as possible. The images of pins A and B were observed in the mirror and the third pin (C)
was moved closer to the mirror so that it was in line with the images of A and B. A fourth pin
(D) was placed close to the edge of the paper so that it was in line with pin C and the images of
pins A and B. All pins were removed and an X was placed over the holes that were used. A line
was drawn through the pinholes of C and D and was extended back to the mirror line (reflected
ray). Arrows were drawn in to indicate the ray paths. The protractor was used to measure the
o
o
o.
o
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angle of reflection, r, and both r and its corresponding angle of incidence, i, was recorded. It was
repeated for all the others in a suitable table.
Data analysis
1. Why were the pins placed as far apart as possible?
●
0.
If the rays do not intersect at one point, what does this indicate?
●
0.
They were placed far apart so they can be more accurate when measuring.
It would be deemed as inaccurate.
List any precautions and sources of error.
●
precautions – the degrees were accurate
●
error – if the mirror had moved
0.
Discuss the results you have obtained, stating clearly what you have found out about the
relationship between the angle of incidence and the angle of reflection.
●
The results showed that the angles were equal.
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MEASURING AREA
34
35
36
ANALOGOUS SYSTEM
Objective
To use an analogous system to illustrate the nature of radioactive decay.
Apparatus
100 coins, large can with lid
Diagram
Procedure
The number of coins present when n = 0 was noted. Heads was used to represent a decayed atom
and tail was used to represent an undecayed atom. The coins were placed into the can and the lid
was snapped on. The can was shaken vigorously, then the lid was removed and the coins were
poured out. The number of tails i.e the number of undecayed atoms t for n = 1 was recorded. The
number of heads were placed to one side (decayed atoms). The undecayed atoms were placed
back into the tin. Steps 3 - 5 were repeated 4 times (until n = 5).
Data collected
Undecayed
Decayed
n=0
100
0
n=1
52
48
37
n=2
23
29
n=3
13
10
n=4
7
6
n=5
2
5
Data analysis
1. Plot a graph of the number of throws (n) on the x-axis against the number of
undecayed atoms (t) on the y-axis.
(i) If your classmates do the experiment, would they get the same results? (ii) If one coin
is marked with an X, can we predict when it will decay? (iii) Complete the following
statement:
Radioactive decay is said to be random because
-
(a) it is impossible to predict when a particular radioactive nucleus will decay
(b) you cannot cause or influence the decay.
2. If we repeat the experiment several times, on average how many coins out of 100
would we expect to decay after one throw? Explain how a radioactive substance is said
to be random and still have a half-life?
3. Use your graph to estimate at least three values for the half-life. Is it constant?
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