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
    ve                                                   sky.
   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.
                   Matter is a substance that has inertia and occupies physical space.
   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