Dear students

You don’t have to write procedure of any of the experiments.

You have to make diagrams on white pages .

This work need to be done in Physics Practical Notebook or Lab Manual of Physics

You need to make the proper diagrams using pencil.

EXPERIMENT-1

Aim
To verify the laws of reflection of sound.

Theory

1. Sound: It is a form of energy produced by vibration and it needs medium to

propagate.
2. Reflection of sound: As light reflects when it strikes any hard object (opaque),
sound also gets reflected when it strikes any object.

Laws of Reflection of sound

1. The angle of incidence is always equal to the angle of reflection.

 2. The incident sound wave, the normal and the reflected sound wave lie in the same
plane.

Materials Required
Two highly polished metal tubes made up of stainless steel or aluminium of length 25
cm and diameter 2 cm, a drawing sheet, metal plate, a geometrical set, thumb pins,
drawing board/table, stopwatch, metal stand.

Procedure

1. Fix the white sheet on drawing board with thumb pin.

2. Draw a line AB to place the metal plate as reflecting surface with the help of metal
stand, and draw normal OP to this line as shown in the figure.
3. Now draw a line OC making an angle of 30° with the line OP.
4. Place one metal tube near to the point O of normal and metal plate on the line OC.
5. Place the ticking watch closer to one end of this metal tube.
6. Now place the second tube so that its one end is near to the point O. Bring your ear close
to the other end and adjust its position such that it colle
 cts the maximum reflected sound.
7. Mark the position of the tube when it collects the clear and maximum reflected sound.
8. Draw an extended line of reflected sound wave and mark it as OD.
9. Measure the angle of incidence and the angle of reflection.
10. Follow the above procedure and record your observation thrice.
11.

Observation Table
Result

1. The angle of incidence is equal to the angle of reflection.

2. The incident, normal and reflected sound waves lie in the same plane.

Precautions

1. The metal plate should be placed vertical on the drawing board.

2. Both the pipes used should be clean and shining.
3. The sound producer i.e. stopwatch should be placed closer to the end of the metallic
tube.
4. Avoid touching of the source of sound to the metal tube.

EXPERIMENT -2

Aim
To determine the density of solid (denser than water) by using a spring balance and a
measuring cylinder.

Theory

1. Density: The density of a substance is defined as the mass per unit volume,

[D= MV]
Here, D = Density of the body
M = Mass of the body
V = Volume of the body.
2. S.I. unit of density = Kgm-3 or Kg/m-3
c.g.s. unit of density = g/cm-3 or g cm-3
3. Floating bodies: The density of water is 1 g/cm3 (c.g.s. system) and 1000
kg/m3 (S.I. system).
4. Case (a) If the density of a body is more than 1 g/cm 3 or 1000 kg/m3 then the body
will sink in water.
5. Case (b) If the density of a body is less than 1 g/cm3 or 1000 kg/m3 then the body
will float on water.
6. Case (b) If the density of a body is less than 1 g/cm3 or 1000 kg/m3 then the body will
float on water.
 7. Case (c) If the density of a body is same i.e. 1 g/cm3 or 1000 kg/m3 then the body will
half float and half submerge in water.

Weight

1. The force due to the gravitational attraction of the earth that acts on a body is
called weight.
2. (Weight) Force = mass x acceleration.
Force = mass x acceleration due to gravity (g)
Force = mass x g
i.e     Weight = m x g
3. Weight of a body = Force on the body.
4. S.I. unit = Newton = 1 kg m/s2
N =1 kgf= 1 kilogram force,
i.e    g = 9.8 m/s2
5. Weight is measured by spring balance

Materials Required
A spring balance, a measuring cylinder, a beaker with water, a metal bob (or any body
that is heavier than water and does not dissolve in water), a cotton string, a stand
(optional).

Procedure

1. Tie a metal bob (or any solid) with the string of cotton to the hook of the spring
balance. The spring balance should be checked for any error. Let the zero error be
‘x’.
2. Hold the spring balance (or tie it to the stand), suspended with the metal bob in air.
Measure the weight of the bob. Let its weight be ‘W F‘
3. Pour the water in the measuring cylinder and record the initial volume of water, let
it be   ‘ V1‘
4. Suspend the metal bob into the measuring cylinder with water. The bob should not
touch the base, nor the sides of the cylinder.
5. Record all your observations in the observation table and do the calculation to
find the density of a given solid metal bob.
 Observations

1. Weight of the given Metal Bob = 400N

2. Mass of the Metal Bob = 400/9.8 = 40.8 g

1. Volume of water displaced by solid (metal bob) = 20 mL.

2. Density of solid (metal bob) = 40.8g20ml = 2.04 g/cm3
1 mL of water = 1 cm3

Result 
The density of given solid (Metal Bob) is 2.04 g/cm3

Precautions

1. The spring balance should be sensitive.

2. The zero error in the spring balance should be recorded before it is used to find the
weight of solid.
3. Record the readings carefully of both spring balance and measuring cylinder by
keeping the level of eye and the mark of reading same/parallel.
4. The solid/metal bob should not touch the bottom, or sides of the measuring cylinder.
5. If the zero error in spring balance is 1 N then subtract this error from the final reading of
the weight of solid/ metal bob.

EXPERIMENT-3

Aim
To establish the relation between the loss in weight of a solid when fully immersed in

1. tap water
 2. strongly salty water, with the weight of water displaced by it by taking at least two
different solids.

Theory

1. Fluids: Gases and liquids flow and are thus called fluids.

2. Buoyancy: The upward force exerted by fluids on any body is called the buoyant
force and this phenomenon is known as buoyancy.
3. Thrust: The force acting on a body perpendicular to its surface is called thrust. S.I.
unit is Newton.
4. Pressure: The thrust per unit area is called pressure.

Pressure =Thrust/Area
S.I. Unit =Nm2 or Nm-2. This unit (Nm-2)is also called  Pascal,
.’. 1 Pascal (Pa) = 1  Nm-2

5. Weight of a body = Mass x acceleration due to gravity

W = mg
6. When a body is immersed in water or liquid, the body displaces some liquid.
7. The volume of liquid displaced = total volume of the solid.
8. The mass of liquid displaced can be measured as:
Mass of liquid displaced = Volume x Density
M=VxD
9. Weight of liquid displaced = Volume x Density x g (acceleration due to gravity)
W=VxDxg
10. The body loses some weight when immersed in fluid, it can be found as follows:
11. Weight of the body in air = W1
Weight of the body when immersed in liquid = W2
12. Hence loss in weight = W2 -W1
How much will be this upward force/buoyant force depends on the density of liquid in
which it is immersed. The upthrust is more by denser liquids.
13. Archimedes’ Principle: When a body is immersed fully or partially in a fluid, it
experiences an upward force that is equal to the weight of the fluid displaced by it.

Materials Required
A spring balance, a metal bob, a cotton thread, an overflow can, a glass beaker, tap
water, salty water, an iron stand.

Procedure
A. Find the zero error and least count of spring balance:

1. Take an iron stand and suspend a spring balance to it.

2. Study the spring balance, its scale and its least count.
 3. Record your observations. If any error, record it as ‘x’ gf.

B. Find the weight of solid metal bob in air:

1. Take a metal bob, tie thread to it and suspend on the hook of the spring balance.
2. Record the weight of the metal bob in air. Let this weight be Wr

C. Find the weight of the metal bob immersed in tap water and record the apparent
loss in weight

1. Take an overflow can, fill it with water such that its water level touches the spout
of the overflow can.
2. Keep an overflow can under the spring balance such that the metal bob gets fully
immersed in the water of
the overflow can.
3. Keep a beaker whose weight P1 is recorded, at the mouth of the spout of overflow
can.
4. As soon as the metal bob is suspended in water the weight on spring balance
scale is recorded. This loss in weight is due to buoyancy (W 2).
5. Collect the water that has overflown in a beaker till the last drop that comes out of
the spout.
6. Weigh the beaker with water (P2).
7. Calculate the weight of the displaced water (P2-P1).
 8. Calculate the loss in weight of the metal bob when immersed in water.

D. Find the weight of metal bob immersed in salty water and record the apparent loss
in weight.

1. Prepare salty water by taking a 500 mL beaker and adding 300 mL of water in it and
dissolving common salt till the saturated solution is obtained.

1. Take the same metal bob and repeat the steps from 1 to 8 as given in procedure
‘C’
2. Tabulate your observations.

Observations and Calculations

1. Zero error in spring balance = (x) = 0 gf.

2. Least count of the spring balance = 2 gf.
3. Density of water = 1 g/cm3
 4. Weight of empty beaker P1= 100 gf.

Conclusion

1. Hence it is proved that the weight of the water displaced by the metal bob is
approximately equal to the apparent loss of weight of the metal bob in water.
Archimedes’ principle is verified.
2. The weight of water displaced by a given solid when immersed fully in strongly
salty water is more than the weight of the water displaced when fully immersed in
tap water.

Precautions

1. Carefully study the spring balance used for the experiment.

2. Fill the overflow can above the mark of the spout, allow extra water to overflow
through the spout without disturbing it. Use this overflow can for the experiment.
 3. Do not allow the suspended solid mass i.e. metal bob/stone to touch the base and sides
of the overflow beaker.

EXPERIMENT-4

Aim
To determine the velocity of a pulse propagated through a stretched string/slinky.

Theory

1. Wave: A wave is a disturbance that moves through a medium when the particles
of the medium set neighbouring particles into motion by transfer of energy.
2. Slinky: A slinky is a long spring which is flexible and has appreciable elasticity.
3. Pulse: A wave produced by a single disturbance in a medium is known as pulse.
Velocity of pulse =Totaldistancetravelledbypulse/Totaltimetaken

Materials Required
A slinky with flat wire made up of metal/plastic should be atleast 1 m long, a metre
scale, a stop-watch, a marker/ chalk.

Procedure
 1. Mark a point on the floor of a long corridor. Let this poi

2. From point P measure the distance of 1 m with the help of metre scale, mark this
point as Q.
3. Allow one student to hold one end of slinky at point P.
4. Let another student stretch the slinky and bring it at point Q.
5. Let third student hold the stopwatch.
6. The student who has stretched the slinky will stretch it beyond point Q and then
give a sharp push towards pointQ. The push should stop at point QA pulse is
produced in the slinky which travels towards the point P and it gets reflected
backtowards point Q.
7. Record the time from push at Q to the pulse travelling towards P and back at Q.
8. Follow the above procedure 56 times and record your observation
9. Calculate the velocity of pulse by the formula
Velocity of pulse = Totaldistancetravelledbypulse/Totaltimetaken
υ =2d/t

Observation

Average velocity of pulse = 0.176+0.198+0.189+0.174+0184/5 = 0.1842

Result
The velocity of pulse = 0.1842 m/s.
Precautions

1. Slinky used should be of good quality and with even springs coiled all over.
2. Accurately measure the distance and time.
3. The push at the end should be forceful to see the pulse and get the reflected wave back.
4. The slinky should not have any knot or kink at any point along its length.