563 - Physics Questions Answers

how far from earth we can see earth as a whole elliptical?{we can clearly see the earth


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Joshi sir comment


for getting the complete vision we should draw tangents at the extreme of major and minor axis of the earth, this will give a point of intersection for which height from centre of earth will be R√2 so height from earth surface will be R√2 - R = R(√2-1)

here R is used for radius of earth

This is approximate calculation only 

A 20 cm long test tube (cylindrical) is inverted & pushed vertically down into the water . when the closed end is at water surface, how high has the water risen inside the tube?  [p atm =10^5 N/m²]

Asked By: AMIT DAS
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Joshi sir comment

Let the height of water in the tube is x cm. then according to PV = constant, calculate the pressure by (20-x) cm. column

then P0 + pressure by 20 cm water = pressure by (20-x) cm. column + pressure by x cm water column 

A body is moving towards north with initial velocity of 13m/s. Its is subjected to a retardation of 2 m/s2 towards south.The distance travelled in 7th sec is ??

is this question helpfull: 14 2 read solutions ( 3 ) | submit your answer
Joshi sir comment

displacement of any particular sec. = u+at-(a/2)

here direction of motion is opposite to the direction of acceleration so formula will be u-at+(a/2) 

displacement in 7th sec = 0

now we know that direction of motion will become south after 6.5 sec. so distance for last half sec = ut+(1/2)at= 1/4

same will be the distance for the first half sec of 7th. so total distance for 7th sec = 1/4 + 1/4 = 1/2


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