1. When a pipe decreases to one half its radius and thepressure decreases by a t
ID: 1680251 • Letter: 1
Question
1. When a pipe decreases to one half its radius and thepressure decreases by a tenth of an atmosphere, what is the speedof the water in the larger pipe? A)1.15m/s B) 1.33m/s C)2.66m/s D) 4 m/s 2. A piece of wood sinks to 50% of its volume in water and to70% of its volume in an oil. What is the density of theoil? A) 750kg/m3 B) 1000kg/m3 C)764 kg/m3 D) 714kg/m3 1. When a pipe decreases to one half its radius and thepressure decreases by a tenth of an atmosphere, what is the speedof the water in the larger pipe? A)1.15m/s B) 1.33m/s C)2.66m/s D) 4 m/s 2. A piece of wood sinks to 50% of its volume in water and to70% of its volume in an oil. What is the density of theoil? A) 750kg/m3 B) 1000kg/m3 C)764 kg/m3 D) 714kg/m3Explanation / Answer
2) By Archimedes' principle, when an object floats in a fluid,it displaces an amount of water that has mass equal to the mass ofthe object. Therefore, if M is the mass of the piece of wood, thenM is the mass of the water displaced. The water displaced has halfthe volume of the wood and has the same mass, so the wood must behalf as dense as water. Water has density 1000 kg/m^3, so the woodhas density 500 kg/m^3.
Now if the volume of the wood block is V, its mass is 500V.The oil displaced has the same mass (500V) and has volume .7V.Therefore, its density is mass/volume = 500V/.7V = 500/.7 = 714kg/m^3.
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