Consider a raindrop falling through a cloud of tiny water droplets. Some of these tiny droplets get attached to this raindrop as it falls increasing its mass. Assume constant growth in the mass of the raindrop as a function of distance x of fall. Find out the acceleration of the raindrop assuming it to be constant.
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Category Archives: Physics
Infinite Grid of Resistors
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There is an infinite wire grid with square cells. The resistance of each wire between neighbouring joint connections is R. Find the equivalent resistance of the whole grid between points x and y. |
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$$v^2-u^2 \neq 2as$$
When a particle is thrown up vertically from the surface of the earth (radius R), we have v2-u2=2(-g)h (h << R) if the effects due to the atmosphere of the earth are neglected (symbols mean the usual things). However, if h << R condition is not applicable, prove that 
Continue reading $$v^2-u^2 \neq 2as$$
High Temperature in a Fusion Lab Quiz
A nuclear fusion lab requires very high temperature for the fusion reaction to take place. Mr X says, “The temperature at Sun’s surface is around 6000 K. We can use advanced lenses/mirrors to focus Sun’s rays and get temperature much higher than 6000 K. Mr Y disagrees. Who is right?
(A) Mr X
(B) Mr Y
(C) Information is insufficient to answer
Parallel Circular Loops Magnetic Flux
A circular loop of radius 0.3 cm lies parallel to a much bigger circular loop of radius 20 cm. The centre of the small loop is on the axis of the bigger loop. The distance between their centres is 15 cm. If a current of 2.0 A flows through the smaller loop, then the flux linked with bigger loop is:
(1) 9.1 x 10-11 weber (2) 6 x 10-11 weber (3) 3.3 x 10-11 weber (4) 6.6 x 10-9 weber
[JEE Main 2013]
A projectile is given an initial velocity of $$\hat i + 2\hat j$$
A projectile is given an initial velocity of 
, where 
is along the ground and 
is along the vertical. If g = 10 m/s2, the equation of its trajectory is:
(1) 
(2) 
(3) 
(4) 
[JEE Main 2013]
Continue reading A projectile is given an initial velocity of $$\hat i + 2\hat j$$
Plano-Convex Lens Having 3 mm Thickness
Diameter of a plano – convex lens is 6 cm and thickness at the centre is 3 mm. If speed of light in material of lens is 
m/s, the focal length of the lens is:
(1) 15 cm (2) 20 cm (3) 30 cm (4) 10 cm
[JEE Main 2013]