NEET Physics Rotational Motion NEET PYQ-Rotational Motion

Three masses are placed on the x-axis: 300 g at origin, 500 g at \[x=40\,cm\] and \[400\,g\] at \[x=70\text{ }cm\]. The distance of the centre of mass from the origin is [AIPMT (M) 2012]

A) 40 cm

B) 45 cm

C) 50 cm

D) 30 cm

Correct Answer: A

Solution :

\[{{x}_{CM}}=\frac{{{m}_{1}}{{x}_{1}}+{{m}_{2}}{{x}_{2}}={{m}_{3}}{{x}_{3}}}{{{m}_{1}}+{{m}_{2}}+{{m}_{3}}}\]

\[=\frac{300(0)+500(40)+400(70)}{300+500+400}\]

\[=\frac{20000+28000}{1200}\]

\[=\frac{48000}{1200}\]

\[=40\,cm\]