While exploring the remnants of an alien civilization you\'ve discovered hidden

Question

While exploring the remnants of an alien civilization you've discovered hidden on one of Saturn's moons, you find a light, tough, springy mystery metal unlike anything you've ever seen. You take a rectangular, 2 cm * 2 cm * 50 cm bar of it to your lander for analysis. When you squeeze the ends together with a force of 1.8 kN, it compresses by 5.0 cm. When you place it in a tank of water, it floats with 50 % of its volume submerged.

a) What is Young's modulus for the material?

b) What is the material's density?

c) At what speed should sound propagate through the material?

Explanation / Answer

Stress= Force/ cross section area = 1.8*1000/2*2*10^-4 = 450000 Pa

Strin = change in length/original = 5/50 = 0.1

a) Young's modulus= Stress/strain = 450000/0.1= 4500000 Pa = 4.5 Mega Pascal

b) Since it floats with half submerged

Rho*V*g = 1000*V/2*g

Rho= 500 kg/m3 (density)

c) Speed = Sqrt ( Young;s modulus/density) = Sqrt( 4500000/500) = 94.87 m/s

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