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' एकूण ऋतू किती ? ' असा प्रश्न तुम्हाला विचारलात तर तुम्ही म्हणाल 'सोप्पंय !  तीन ऋतू आहेत , हिवाळा,  उन्हाळा आणि पावसाळा…… '  हे झाले पुस्तकी उत्तर, पण गेल्या चार ते पाच वर्षात झालेल्या वातावरणातील बदल पहिला तर आपल्या लक्षात येईल कि हे  ऋतूचक्रही बदलत चालले आहे.
                     

Prove that the angle between the surface of an inclined plane and a the horizontal (the angle of inclination) is equal to the angle between the normal of the plane and the vertical.

Prove that the angle between the surface of an inclined plane and a the horizontal (the angle of inclination) is equal to the angle between the normal of the plane and the vertical.

The angle between the surface of an inclined plane and a the horizontal (the angle of inclination) is equal to the angle between the normal of the plane and the vertical.

Two charges of equal magnitude q are placed in air at a distance 2 a apart and third charge -2q is placed at mid – point. The potential energy of a system is? ( ԑo = permittivity of free space ) . (MHT-CET ~ 2014)

Two charges of equal magnitude q are placed in air at a distance 2 a apart and third charge -2q is placed at mid – point. The potential energy of a system is? ( ԑ_o = permittivity of free space ) . (MHT-CET ~ 2014)

a ] - q ² / ( 8 π ε _o a )                        b] - 3 q ² / ( 8 π ε _o a )                     

c] – 5 q ² / ( 8 π ε _o a )                     d] - 7 q ² / ( 8 π ε _o a )

Two concentric sphere kept in air have radii R & r . they have similar change and equal charge density σ. The electric potential at their common centre is? ( MHT - CET ~ 2014 )

Two concentric sphere kept in air have radii R & r . they have similar change and equal charge density σ. The electric potential at their common centre is? ( MHT - CET ~ 2014 )

a ]  σ ( R + r ) / ε _o            b ] σ ( R – r ) / ε _o

c ] σ ( R + r ) / 2 ε _o               d ] σ ( R + r ) / 4 ε _o

Black Body Radiation

If the temperature of black body is increased by a factor of 2, the amount of energy and volume radiated increases by a factor of . . . . . . . . . .

( a ) 2               ( b ) 4               ( c ) 8               ( d ) 16

Acceleration due to Gravity; The ratio of escape velocity on the Earth to that on Mars.

The acceleration due to gravity ( g ) on the surface of the Earth is approximately 2 . 6 times that on the surface of the Mars . Given that the radius of Mars is about one half the radius of the Earth , the ratio of the escape velocity on Earth to that on Mars is approximately . . . . . . . . . . .

a ) 1 . 1
b ) 1 . 3
c ) 2 . 3
d ) 5 . 2 

The angle between vector ( i + j ) and ( j + k ) is ( in Radian )

The angle between vector ( i + j ) and ( j + k ) is ( in Radian )

solution :  -

Let us consider

A = i + j

B = j + k

To find out the