A lead pencil consists of a cylinder of wood with a solid cylinder of graphite filled into it. The diameter of the pencil is 7mm, the diameter of the graphite is 1mm and the length of the pencil is 10cm.Calculate the weight of the whole pencil, if the specific gravity of the wood is 0.7 gm/cm^3 and that of the graphite is 2.1 gm/cm^3.
Answers
Answer:
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Answer:2.805gm
Step-by-step explanation:
ANSWER
We have
Diameter of the graphite cylinder =1mm=
10
1
cm
Radius =
20
1
cm
Length of the graphite cylinder =10cm
Volume of the graphite cylinder =(
7
22
×
20
1
×
20
1
×10)cm
3
Weight of graphite = Volume × Specific gravity
Weight of graphite =(
7
22
×
20
1
×
20
1
×10×2.1)gm
=(
7
22
×
20
1
×
20
1
×10×
10
21
)gm=0.165gm
Diameter of pencil =7mm=
10
7
cm
Radius of the pencil =
20
7
cm and length of pencil =10cm
Volume of pencil =
7
22
×
20
7
×
20
7
×10cm
3
Volume of wood =(
7
22
×
20
7
×
20
×10− 7 22 × 201 × 20 1 ×10)cm
3
Volume of wood = 22 7× 20 1 × 20 1 ×10(7×7−1)cm 3 = 7 11 × 20 1 ×48cm 3
Weight of wood =( 7 11 * 20 1 ×48×0.7)gm =( 7 11 × 20 1 ×48× 10 7 )gm=2.64gm
Total weight =(2.64+0.165)gm=2.805gm