A bottle has a thin nozzle on top. It is filled with water, held horizontally at a height of 1 m and squeezed slowly by hands so that the water jet coming out of the nozzle hits the ground at a distance of 2 m . If the area over which the handss s sare which the hands squeeze it is 10 cm 2 , the force applied by hands is close to (take g = 10 m / s 2 and density of water = 1000 kg / m 3 )

Question

A bottle has a thin nozzle on top. It is filled with water, held horizontally at a height of 1 m and squeezed slowly by hands so that the water jet coming out of the nozzle hits the ground at a distance of 2 m . If the area over which the handss s sare which the hands squeeze it is 10 cm 2 , the force applied by hands is close to (take g = 10 m / s 2 and density of water = 1000 kg / m 3 ), 20 N, 10 N, 5 N, 2 . 5 N

MARKS App · Accepted Answer

Apply Bernoulli between point- 1 and point- 2 . P 1 + 1 2 ρ V 1 2 = P 2 + 1 2 ρ V 2 2 P 1 = P atm + Force by hand Area V 1 tends to zero becomes area of point- 2 is very small. P 2 = P atm P atm + F / A = P atm + 1 / 2 ρ V 2 2 ⇒ V 2 2 = 2 F P A … i From Kinematics. 2 = 2 ( h ) g × V 2 ∴ V 2 2 = 20 … ii Using (i) and (ii) we get 20 = 2 F ρ A ∴ F = 10 N

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