Question

Two objects of masses 300 g and 700 g possess velocities `15 hat"i"` m/s and `4 hat"i" + 6 hat"j"` m/s respectively. The velocity of their centre of mass in m/s is:

विकल्प

• `7 hat"i" + 8 hat"j"`

• `7.3 hat"i" + 4.2 hat"j"`

• `5 hat"i" + 4 hat"j"`

• `2 hat"i" + 6 hat"j"`

Answer 1

`7.3 hat"i" + 4.2 hat"j"`

Explanation:

`overline"V""cm" = ("m"_1 vec("v"_1) + "m"_2 vec("v"_2))/("m"_1 + "m"_2)`

= `(300(15 hat"i") + 700(4 hat"i" + 6 hat"j"))/(300 + 700)`

`overline"V""cm" = (4500 hat"i" + 2800 hat"i" + 4200 hat"j")/1000`

= `(7300 hat"i" + 4200 hat"j")/1000`

`overline"V""cm" = 7.3 hat"i" + 4.2 hat"j"`