Three masses are placed on the x-axis : `300 g` at origin. `500 g` at `x = 40 cm` and `400 g` at `x = 70 cm`. The distance of the centre of mass from the origin is.

Options

A. 40 cm
B. 45 cm
C. 50 cm
D. 30 cm

Answer

A

Explanation

Distance of the centre of mass from the origin,
`x_("CM")=(m_(1)x_(1)+m_(2)x_(2)+m_(3)x_(3))/(m_(1)+m_(2)+m_(3))`
`=(300(0)+500(40)+400(70))/(300+500+400)`
`=(20000+28000)/(1200)=(48000)/(1200)=40cm`