Question

The momentum of a body is $20,000$ dyne-sec. If Its K.E is $200$ ergs, the mass of the body is:

• A. $100kg$
• B. $200kg$
• C. $2000kg$
• D. $1000kg$

Answer 1

The correct option is D $1000kg$

K.E $=\frac{1}{2}m{v}^2$

$=\frac{1}{2}\frac{(mv{)}^2}{m}=\frac{1}{2}\frac{p^2}{m}$

$m=\frac{1}{2}\frac{p^2}{K.E}=\frac{1}{2}\frac{(2000{)}^2}{200}$

$m=\frac{400000000}{400}=1000000g$

$m=1000kg$