Question

A block of mass $10\text{kg}$ lies on a rough plane as shown in the figure. A constant force $F$ is applied for $10$ seconds, find out the value of work done by the force $F$.

• A. $12000\text{J}$
• B. $10000\text{J}$
• C. $-6000\text{J}$
• D. $0\text{J}$ (because friction is present)

Answer 1

The correct option is A $12000\text{J}$

FBD of Block
Net force in vertical direction
$N-mg=0$
$N=mg=10\times 10=100\text{N}$

Frictional force $=\mu N$
$=0.2\times 100$
$=20\text{N}$

Net force in horizontal direction
$=F-\text{Frictional force}$
$ma=60-20$
$a=\frac{40}{10}=4{\text{m/s}}^2$
Applying ,
$s=ut+\frac{1}{2}a{t}^2=0+\frac{1}{2}\times 4\times {10}^2$
$s=200\text{m}$
Work done by force $W=F.s=60\times 200$
$=12000\text{J}$