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A rock is suspended from a scale reads 15.0 N. A beaker of water (having a densi

ID: 1628687 • Letter: A

Question

A rock is suspended from a scale reads 15.0 N. A beaker of water (having a density of 1000 kg/m^3) is raised up so the rock is totally submerged in the water. The scale now reads 5 N. What is the buoyant force?_____________ What is the density of the rock? _____________ Water is flowing in a horizontal pipe of radius 1 m. Suppose you want to change the diameter of this pipe so that the speed of the water would be half as great as it was, what should be the new radius? ____________ The gravitational acceleration on the surface a planet you just discovered is 18.0 m/s^2? What is the gravitational acceleration at an altitude of one planet diameter above the SURFACE of the planet? __________ Suppose you found a second planet where the gravitational acceleration on its surface is half that of the first planet (9 m/s^2). What is the ratio of the mass of the first planet to the second planet? ___________ A 100-kg object is released from rest at an altitude of 2R above the north pole of the earth. If we ignore atmospheric friction, with what speed does the object strike the surface of the earth? Give your answer in terms of G, R and M_earth (the polar radius of the earth is R) __________ An object of mass 1.0 kg is attached to an ideal massless spring and allowed to hang in the Earth's gravitational field. The spring stretches 4 cm before it reaches its equilibrium position. If this system is allowed to oscillate, What is the spring constant ? What will be its frequency?

Explanation / Answer

Question 6 ) using the formula

A1*v1 = A2*v2

Given , A1 = *r^2 , since r = 1 m

A1 = *1^2 = 3.1416 m^2

Let, v1 = v , so v2 = v/2( it is given in question that velocity is half the initial velocity)

Since A1*v1 = A2*v2

3.1416*v = *r^2*v/2

r^2 = 3.1416*2/ = 2

r = 1.414 m

Therefore, radius = 1.414 m

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