MOTION, MOTION IN LIQUIDS, MOTION IN SOLIDS, ARCHMEDES PRINCIPLE, CENTRIPETAL FORCE, FORCE BASIC CONCEPTS

1. MOTION AND LIQUIDS
PREPARED BY
V.REVATHIAMBIKA
7/28/2012 LECTURER IN PHYSICS
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3. MOTION
• A change in the position of a body or
system with respect to time, as
measured by a particular frame of
reference. Only relative motion can
be measured; absolute motion is
meaningless.
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4. INFERENCE
1. A body is said to be in the state of rest when it
remains in the same position with respect to
time.
2. A body is said to be in the state of motion, when
it continuously changes its position with respect
to time.
3. The distance between the two places is not the
same; it depends upon the path chosen.
4. The shortest distance, or distance travelled
along a straight line, is known as displacement.
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5. MOTION CLASSIFICATION
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6. Motion Classification
• If an object
covers equal
Uniform distances in equal
interval of time
• If an object
Non- covers unequal
Uniform distances in equal
interval of time
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7. Measuring the rate of motion
Speed Displacement
The distance The distance
travelled in one covered when
second or rate of travelled along a
distance travelled. straight line.
Total distance travelled Total covered distance
Time taken Time taken
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8. Rate of
motion
Velocity Acceleration
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9. VELOCITY ACCELERATION
It is the displacement made in one It is the change in velocity of an
second or rate of change of object per second or rate of change
displacement. of velocity.
DISPLACEMENT CHANGE IN VELOCITY
TIME TIME TAKEN
UNIT : meter/ second UNIT : meter / second2
Uniform velocity : Uniform Acceleration :
Equal distance covered by a body If an object travels in a straight line
in equal intervals of time and its velocity increases or
decreases by equal amount in
equal intervals of time, then the
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acceleration of the object is 9
uniform.

10. GRAPHICAL EQUATION OF MOTION
1. Equation for Velocity at a time
v = u + at
2. Equation for displacement
s = ut + ½ at2
3. Equation for velocity at a position
v2 = u2 + 2as
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11. Acceleration due to gravity
♣ When a the body is allowed
to fall down, the velocity
gradually increases. Now the
body is accelerated.
♣ The deceleration or
acceleration due to the
gravitational force of earth is
known as acceleration due to
gravity.
It is denoted by “ g”
The value of “ g” is 9.8 m/s 2
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12. Uniform circular motion
 Circular motion :
An athlete runs along the circumference of a
circular path or The movement of an object in a
circular path
 Uniform circular motion :
When an object moves in a circular path with a
constant velocity.
The magnitude of the velocity is constant at all
points and the direction of the velocity changes
continuously.
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13. • Angular displacement :
The angle covered by the line joining the body and
the centre of the circle.
It’s measured in radian
• Angular velocity :
The angular displacement in one second or Rate of
change of angular displacement.
Angular displacement
time taken
ω = θ/ t
UNIT : radian / second
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16. CENTRIPETAL FORCE
• The constant force that acts on the body along
the radius towards the centre and perpendicular
to the velocity of the body.
•F = mv
/r2
• F = mrω 2
• Since v = rω
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17. MOTION IN LIQUIDS
• When a body floats or
immerses in a liquid, the
pressure on the bottom
surface is more than that the
pressure on the top of the
surface.
• Due to the difference in
pressure, an upward force
acts on the body.
• This upward force is called
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18. Centre of buoyancy
• The upward force is called upthrust or
buoyant force.
• The buoyant force (upthrust) acts through the
centre of gravity of the displaced liquid which
is known as centre of buoyancy.
• The buoyant force is equal to the weight of
the liquid displaced.
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19. Archimedes principle
• When a body is
immersed in fluid (liquid
or gas) it experiences an
apparent loss of weight
which is equal to the
weight of the fluid
displaced.
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21. Relative density
• Density :
Density of a body is defined as the mass per unit
volume of the body.
Mass
Volume
UNIT : Kg / m
Relative density :
It is defined as the ratio of density of the body to
the density of water.
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22. Laws of flotation
• The weight of the floating body is
equal to the weight of the liquid
displaced by it.
• The centre of gravity of the floating
body and the centre of gravity of the
liquid displaced (centre of buoyancy)
are in the same vertical line.
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23. HYDROMETERS
There are two types of hydrometers
1. The constant immersion hydrometer, in which the
weight of the hydrometer is adjusted to make it
sink to the same fixed mark in all liquids.
2. The variable immersion hydrometer, in which the
weight of the hydrometer remains the same, but
the depth to which it sinks in different liquids
vary.
3. A common hydrometer used to test the purity of
milk by noting its specific gravity is called a
LACTOMETER.
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