Question

A cubical block of wood of side 5 cm is placed on a table. Find the thrust by the block of wood on the table, if density of wood is $5gc{m}^{-3}$ and g is $10m{s}^{-2}$

• A. 4.25 N
• B. 5 N
• C. 6.25 N
• D. 7 N

Answer 1

Answer: (C)

6.25 N

Given

Block side $a=5cm$

Wood density $d=5g/c{m}^3$

Volume of the cubical block with side ' a ' cm, $v=a^{3}c{m}^3$

so volume of cube with side length 5 cm $=(5cm{)}^3=125c{m}^3$

As we know, Density = $\frac{Mass}{Volume}$

Mass $=Density\times volume$

so mass of the cube $M=5\times 125=625g=0.625kg$

From FBD of table,

Force applied by the block on the table will be equal to the normal force that is equal to $N$.

From FBD of block,

$N=mg=0.625\times 10=6.25N$

Hence Thrust force on the table by woodblock will be equal to 6.25 N

so option (C) is correct