law [law of
inertia]: An object remains in the state of
rest or uniform motion till a force
compels it to change that state. Tendency of objects
to stay at rest or keep moving
when a bus
starts motion our body is pulled backwards as it is at
rest and the feet and bus are in motion.
When a bus
applies brakes the body moves forward as it’s in
motion but the feet and the bus are in rest.
When a car takes
a turn our body swings as it was in a straight line
When we make a
heap of carom coins and take a striker and hit them
then the lowermost coin moves, but the remaining heap
falls in place due to inertia.
is present in
all objects; more the mass more is the inertia. Hence
mass is a measure of
law: The rate of
change of momentum of an object is proportional to the
applied unbalanced force
which is in the direction of the force.
cricketer catching a ball pulls his hand back to
increase the time his hand
takes to reduce the speed of ball to zero.
also jumps on a cushion to increase the time his body
would take to
reduce its speed to zero.
karate artist breaks a slab of ice with a single blow
using same principle.
4.A small bullet
can kill a man if its momentum
is great, a heavy truck moving a smallspeed can kill a man easily sue to it momentum.
Every action has an equal and opposite reaction.
when a bullet is
fired, the force by which it moves forward causes recoil
of the gun. When the
sailor jumps forward, his boat moves backwards.
Energy and types of Energy
possessed by an object by virtue of its motion.
energy is possessed
by an object by virtue of its position or configuration.
of potential and kinetic energy is called Mechanical
is the rate at
which work is done. [Unit = watt] Commercial unit of
energy is kilowatt hour,
thus electrical energy used by an appliance in a month
is in kilowatt hour this
is also expressed in terms of “unit”.
when we stretch a
bow the potential energy that is stored in it gets
transferred into kinetic
when the bow is released. When an object is raised it
potential energy due to the work done in raising it.
Fig 1: Types of energy
1790 French came up
with a standard system of measurements. High speed winds
are accompanied by
reduced air pressure.
period [time to
complete one oscillation] of a pendulum of a given
length is constant. Pendulum
were discovered by Galileo Galilee
Galilee: proposed a new
design to the telescope. Designed barometer and
pendulum. Discovered moons of
Jupiter and the sunspots. He said all planets revolve
around the sun not earth.
First law: Orbit of planets is ellipse with Sun as a foci.
Second law: Line joining the planets and the sun sweeps equal areas in equal intervals of time.
Third law: Cube of the mean distance is equal to square of the time period.
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