TOPPER’S COACHING CENTRE
PHYSICS
CH-8
BELGAUM
CLASS -IX
MOTION
 Motion-when an object changes its position with respect to
time then it is said to be in motion.
 Rest-when an object does not changes its position with respect
to time then it is said to be in rest.
 There is not an object which is at absolute rest. Rest and
motion are relative terms. A body appearing to be at rest to
one person may appear to be in motion to another person.
 Distance-it is actual path taken by an object to reach from one
point to other. Its SI unit is metre.
 Displacement-it is shortest path taken by an object to reach
from one point to other .its SI unit is also metre.
 Distance and displacement cannot be same in all cases.
 Magnitude of displacement is usually lesser than the
magnitude of distance except when body is moving in a
straight line. In that case, the magnitudes of two are equal.
 Displacement can be negative, positive and zero. But distance
cannot be negative.
 Speed-distance travelled by an object in unit time is called as
speed. Its SI unit is m/s. It is a scalar quantity because it has
only magnitude .
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There are two types of motion1. Uniform speed AND
2. Non uniform speed
 1. Uniform speed- when an object covers equal distances in
equal intervals of time then motion of that object is said to be
uniform speed.
 2 .Non-uniform speed- when an object does not cover equal
distance in equal intervals of time then motion of that object
is said to be in non-uniform speed.
 Velocity- displacement per unit time is called as velocity. It is a
vector quantity because it has both magnitude and direction.
 Acceleration- rate of change of velocity is called as
acceleration.
 Acceleration=velocity/time
 Si unit of acceleration = si unit of velocity/si unit of time
=m/s/s=m/s2
 Acceleration can be both positive and negative.
 Negative acceleration is also called as deceleration. Its unit is
also m/s2
GRAPHS
 Distance-time graph
 The slope of distance-time graph gives velocity.
 Velocity-time graph
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 The slope of velocity-time graph gives acceleration.
 The area between velocity-time graph gives distance
traversed.
 Equations of motion1 .v=u+ at
2 .s=ut+1/2at
3 .v2-u2=2as
 QUESTIONS TO KILL THE QUESTIONS
1. A stone is thrown in vertically upward direction with a velocity
of 5m/s. The acceleration n of the stone during its motion is 10
m/s2 in the downward direction. What will be the height
attained by the stone and how much time will it take to reach
there?
2. A ball is gently dropped from a height of 20 m .if its velocity
increases uniformly at the rate of 10m/s2 ,with what velocity it
will take to strike the ground ?after what time will it strike the
ground?
3. An artificial satellite is moving in circular path orbit of radius
42250km.calculate its speed if it takes 24 hours to revolve
around the earth.
4. A body completes half of circle in 5s.what is the distance
covered,
its displacement, speed, velocity if
the radius of circle is 15 cm?
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