General Science - 4

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201) The Refractive index of Diamond is 2.41

202) Density of diamond is 3.51gm/cm3

203) Density of graphite is 2.25gm/cm3

204) Third form of carbon is discovered in 1996 by “HW.KROTO”; “Resmasy”. C60.

205) Distance between two layers in graphite is 3.35Ao

206) C-C bond length is 1.42 A⁰  in graphite.

207) C-C bond length is 1.52 Ao in diamond.

208) Radioactivity was discovered by Henry Bequerel in 1896.

209)To avoid overturning of a vehicle moving on a curved road , the height of center of gravity of vehicle must be nearer to the ground.

210)When a spin bowler throws a cricket ball towards the batsman , the center of mass of ball follows a parabolic path.

211) Newton’s laws of motion apply only to centre of mass.

212) A body is heated uniformly keeping it on a smooth surface . the position of center of mass wrt that body does not change in position.

213)Two balls are thrown simultaneously in air the acceleration of centre of mass of those two balls in air is equal to ‘g’.

214)If two particles initially at rest approach each other due to mutual force, they two meet at center of mass of system.

215) The center of mass of Earth and moon describes elliptical path.

216)When a person walks on a rough road , the frictional force exerted by the road on him is along his direction of motion.

217) Less mileage is obtained per litre of fuel by a car making frequent stops. Here st each time of starting it has to overcome static friction.

218) Small brake and large brake both are equally effective in stopping a cycle as friction doesn’t depend on area of contact.

219)Coefficient of friction can be greater than 1.

220)When a person walks on a rough surface reaction of force applied by a man on surface  keeps him moving.

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