```Escape Velocity                                                The escape velocity at a given height is
2 times the speed in a circular orbit at
   It is the speed at which the kinetic energy                 the same height.
plus the gravitational potential energy of
an object is zero.                                     Kepler"s Laws
   For a spherically symmetric body, the
escape velocity at a given distance is                 Johannes Kepler developed three laws which
calculated by the formula                              described the motion of the planets across the
2GM
    ve                                                   sky.
r
   Where G is the universal gravitational                 1. Law of Orbits: It state that all planets
constant (G = 6.67×10−11 m3 kg−1 s−2), M
move in elliptical orbits, with the sun at
the mass of the planet, star or other body,
and r the distance from the center of                       one focus.
gravity.                                               2. Law of Areas: It states that a line that
connects a planet to the sun sweeps out
n escape  11.2 km/ s                    equal areas in equal times.
3. Law of Periods: It states that the square of
1         GMm
m n2                            the period of any planet is proportional to
Earth            2           r
2GM                      the cube of the semi major axis of its orbit.
n escape 
r                      P2  a3
   The Escape velocity on the earth’s surface             Kepler"s laws were derived for orbits around
is 11.2 km/s and on the moon’s surface 2.4             the sun, but they apply to satellite orbits as
km/s.                                                  well.
GENERAL PROPERTIES OF MATTER
Matter is a substance that has inertia and occupies physical space.
Elasticity
   It is the property of a material whose                 Stress (σ)
dimensions can be changed by applying a
force to it (for example, pushing, pulling,                The stress applied to a material is the force
twisting,      or        compressing),       but            per unit area applied to the material.
Force F
subsequently returns to its original shape.                  Stress ()         
                   Area A
   The deforming force is called a stress, and
    Where, Stress = stress measured in Nm-2
the deformation is called the strain.
or pascals (Pa)
Plasticity                                                     F = force in newtons (N)
    A = cross-sectional area in m2
   It is the deformation of a (solid) material
undergoing non-reversible changes of                   Strain (ε)
shape in response to applied forces.
   Plastic deformation is observed in most                    It is the relative change in the shape or
materials including metals, soils, rocks,                   size of an object due to externally-applied
concrete, foams, bone and skin.                             forces.
Extension L
     Strain ()           
Lenght    L
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