Stu. No.: Physics 117.3 Midterm Test February 16, 2012 Page 6 B2. A block of woo
ID: 1872264 • Letter: S
Question
Stu. No.: Physics 117.3 Midterm Test February 16, 2012 Page 6 B2. A block of wood, with density 700 kg/m, has a cubic shape with sides 0.330 m long. A rope of negligible mass is used to tie a piece of lead (density 11300 kg/m2) to the bottom of the wood. The lead pulls the wood into the water (density of 1000 kg/m) until the block of wood is just completely covered with water. (a) Calculate the volume of the wood block in m. (1 mark) (b) Calculate the mass of the wood block in kg. (1 mark) Since lead is so dense, assume for a quick first order answer that the volume of lead is negligible compare to the volume of the block of wood. With this approximation, use Archimedes' principle to obtain an approximate value for the mass of the piece of lead. If you did not obtain an answer for (a), use a value of 3.60 × 10-2 m3. (3 marks) (c)Explanation / Answer
(A) Volume = 0.330^3
= 0.036 m^3
(B) mass = volume x density = 0.036 x 700
= 25.2 kg
(C) Fb - m g = 0
(0.036 x 1000 )g - (25.2 + m) g = 0
m = 36 - 25.2 = 10.8 kg ......Ans