Experiment No: 2

VELOCITY OF A PULSE
AIM
To determine the velocity of a pulse propagated through a slinky.

APPARATUS
stopwatch, a slinky (helical spring) and a meter scale.

THEORY
A pulse is a single disturbance, suddenly created, moving through a medium from
the free end to another end (which may be free or fixed) for a short while. The
distance travelled by the pulse in unit time is called pulse velocity.

Pulse velocity (v) = Distance traveled by the pulse (s)

Time taken (t)

PROCEDURE
1. Tie one end of the slinky to a rigid support and measure its length. Let it be (s).
2. Hold the free end of the slinky and create a disturbance up and down vertically,
in case of a transverse wave as shown in figure (a) or vibrate in a back and forth
manner in case of a longitudinal wave as shown in figure(b).
3. A pulse will be formed and it will travel towards the fixed end. Introduce a wave
in the slinky by creating a large number of pulses at regular intervals .
4. Start the stopwatch at the instant when you create the single disturbance to
the first coil and stop the stopwatch at the instant when the last pulse
reaches the fixed support.
5. Record the time (t) taken by the pulse to travel along the slinky of length (s).
6. Repeat the experiment 4-5 times by varying the number of pulses and record
your observations for the time taken (t)
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PRECAUTIONS
1. One end of the slinky should be properly fixed with the rigid support.
2. Slinky should be mass less, flexible and of proper length.
3. Special attention should be paid while recording the time because variations of
time may vary the velocity of the pulse to a higher level.
NOTE to the Student:

The following content should be on the un ruled side of the Journal

PULSE IN A SLINKY

OBSERVATIONS

Length of the slinky =

Least count of the stopwatch =

2
 S.No. Distance travelled by the pulse Time taken Pulse velocity

s(m) t(sec) v = s/t (m/s)

1.

2.

RESULT
The velocity of the pulse propagated through the slinky

EXPERIMENT 3

DENSITY OF A SOLID

AIM
To determine the density of a solid, denser than water using a spring balance and a
measuring cylinder
APPARATUS
A metallic object, an iron stand, a spring balance, a measuring cylinder.
THEORY
Mass per unit volume of a substance is its density. Let M be the mass of the object
and V its volume. Then density ρ is given by the formula

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Mass per unit volume of a substance is its density. Let M be the mass of the object
and V its volume. Then density ρ is given by the formula
ρ=M
V

Let,
The weight of the object measured in air using a spring balance = W1 g wt.
Mass of the object = M gms
Initial volume of water in the measuring jar = V1 ml
Final volume of water in the measuring jar when the solid is
Completely immersed = V2 ml

Density of the object = MASS .

VOLUME

PROCEDURE
 Hung the spring balance vertically with the help of an iron stand.
 Determine its least count.

MEASUREMENT OF WEIGHT OF THE GIVEN SOLID

1. Hung the metallic object to the lower hook of the spring balance and take the
reading

2. Repeat the experiment thrice and determine its mean weight.

MEASUREMENT OF VOLUME OF THE GIVEN SOLID
1. Pour some water in the measuring cylinder and record the initial level of
water. (Lower position of the meniscus)
2. Remove the metallic object from the spring balance and tie it by a thin strong thread
and immerse it completely in the water in the measuring cylinder.
3. The level of water in the measuring jar rises and note the new reading.
4. Difference between the two readings will give the volume of the given solid.
5. Repeat the experiment and calculate the mean value
PRECAUTIONS
1. Spring balance should be sensitive, stable and error free
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 2. The horizontal pointer should move freely along with the scale of the spring
balance.
3. Spring balance must be suspended vertically from fixed support of the iron stand.
4. Reading should be taken only when the oscillations of the hanging object dies
off completely
5. While measuring the volume of the object, the solid should not touch the sides
or bottom of the measuring jar.
6. Our eye should be in the proper level of meniscus while measuring the volume
of the solid object.
RESULT
Density of the given solid (denser than water) = _______ Kg/m3

NOTE to the Student:

The following content should be on the un ruled(blank side) side of the Journal

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MEASUREMENT OF WEIGHT OF THE GIVEN SOILD
OBSERVTIONS
Least count of the spring balance = gwt

Initial reading of the Final reading of the Weight of the given

spring balance spring balance solid
W1 gwt W2 gwt (W2-W1) gwt

Mean weight of the given solid = gwt

Mass of the solid = Gm

Least count of the measuring cylinder = ml

No Initial reading Final reading Volume of the object

V1 ml V2 ml V2-V1 ml

Mean volume of the object (V 2 – V1) = ml

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CALCULATIONS
Mass of the object
Volume of the object = gm
Density of the given object = ml
= Mass of the object
Vol of the object
=
= gm/cc x 1000
= kg / m3

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 Multiple choice questions
1. The
correct experimental set up to verify Archimedes’s principle is

A B A B C D

(1) A
(2) B
(3) C
(4) D
2. A given solid is weighed in air using a spring balance. It is then weighed by
immersing it completely in each of the three vessels containing water as shown.

A B C
Its weight when immersed will be
(1) Equal in all the vessels
(2) Least in vessel A
(3) Least in vessel B
(4) Least in vessel C

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3. The readings on the spring balance for the same solid will be

Water water water

(1) Equal in all the cases A, B and C
(2) Equal in cases A and C only
(3) Equal in cases B and C only
(4) Equal in cases A and B only
4. A student notes down the readings on the spring balance while taking the weight of
the solid in air and the weight of the solid when immersed in a measuring cylinder
containing water.

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The buoyant force exerted on the solid will be
(1) 65 gf
(2)35 gf
(3) 30 gf
(4) 100 gf

5. The spring balance shown here is used to measure the weight of a given solid.

The least count of the spring balance is

(1) 1.25 gf
(2) 1.20 g f
(3) 10 gf
(4) 2.5 gf

Experiment No: 4

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 BUOYANT FORCE
AIM
To establish the relation between the loss of weight a solid when fully immersed in
(i) tap water
(ii) strongly salty water, with the weight of liquid displaced by it by taking
at least two different solids.
APPARATUS
A spring balance, a clamp stand, two different solids, overflows can, tap water,
strongly salty water, a strong thread, two empty beakers.
THEORY
According to Archimedes’ principle, when a body is immersed in a fluid, wholly or
partially
it loses its weight. This loss in weight is equal to the weight of the liquid displaced by
the
immersed part of the body.
The loss in weight is due to the presence of upthrust which is equal to the weight
of the liquid displaced.
Loss in weight = weight of the body - weight of the body when immersed in water

PROCEDURE
MEASUREMENT OF APPARENT LOSS IN WEIGHT OF THE SOLID IN TAP WATER
(i) Measure the weight of the solid in air by using spring balance.
(ii) Weigh the empty beaker by using the spring balance

(iii) Set the spring balance, overflow can with tap water and beaker as shown in
(iv) the figure.

(v) Now allow the solid to immerse completely in water taken in the overflow
can.

(vi) Note down the reading in the spring balance. The difference between the readings
in step 1
(vii) and v gives the loss of weight of the solid in tap water.

(viii) Weigh the beaker containing displaced water. Subtract the reading from the reading
(ix) taken in step (ii). This will give the weight of water displaced.

(x) The weight of water displaced is found to be equal to the loss of weight of the
(xi) solid in water.

PREPARATION OF STRONGLY SALTY WATER

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 (i) Take 500 ml beaker and pour 300 ml of tap water in it
(ii) Dissolve the common salt in water till the solution becomes fully saturated
EXPERIMENT WITH SALTY WATER
(i) Repeat the experiment using salty water
(ii) Tabulate the readings and it is found that loss of weight of the solid in
(iii) salty water is equal to the weight of salty water displaced.

PRECAUTIONS
(i) Should use a stable, sensitive spring balance without zero error.
(ii) Solid body should be immersed completely in tap water and salty water
(iii) while taking the reading.
(iii) Solid should not touch the sides or bottom of the overflow can.
(iv) There should be no air bubble present in the tap water or salty water while taking
(v) the weight of the solid.
RESULT
(i) The apparent loss in weight of the solid in tap/salty water is equal to the weight of
(ii) tap/ salty water displaced.
(iii) Loss of weight of the solid in salty water is more than that in tap water.

NOTE to the Student:

The following content should be on the unruled side of the Journal

MEASUREMENT OF WEIGHT

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OBSERVATIONS AND CALCULATIONS
Least count of the spring balance =
Range of the spring balance=
Density of water = 1 gm/cc
VERIFICATION OF APPARENT LOSS IN WEIGHT OF THE SOLID IN TAP
WATER

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No
. Weight of Weight of Loss of Weight of the Weight of the Weight of tap Verification
the body in the body in weight empty beaker beaker containing water
air tap water gm wt gm wt displaced water displaced A =B
gm wt gm wt. (A) gm wt gm wt (B)
Loss of weight
= Weight of
water displaced.

VERIFICATION OF APPARENT LOSS IN WEIGHT OF THE SOLID BODY IN SALTY WATER

No Weight of Weight of Loss of Weight of the Weight of the Weight of Verification

the body in the body in weight empty beaker beaker containing salty water
air salty water gm wt gm wt displaced water displaced A =B
gm wt gm wt (A) gm wt gm wt(B)
Loss of
weight =
Weight of
water
displaced.

Multiple choice questions

1. Buoyant force
1. Is exerted by a fluid on an object immersed in it
2. Reduces the weight felt by the object
3. Increases with increase in density of the fluid
4. All of these

2. Adding salt to water will

1. Decrease its density
2. Increase its density
3. Does not affect its density
4. None of the above

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3. If upthrust and weight of a liquid displaced when a solid is immersed in it are U and W respectively, then
1. U = W
2. U > W
3. U < W
4. W = 2 U

4. If the up thrust on a body when immersed in tap water and salty water are U A and UB respectively, then
1. UA = UB
2. UA >UB
3. UA < UB
4. (4)UA= 2UB

5. When a body is immersed in a liquid, the forces acting on it are

1. Weight
2. Upthrust
3. Weight and upthrust
4. (4)Neither weight nor upthrust

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