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Two particles are fired together along a smooth horizonta...

Two particles are fired together along a smooth horizontal surface with velocities 4 m/s and 5 m/s. If they move at 60° to each other, find the distance between them in 2 seconds.

A.

261

B.

42

C.

221

D.

210

Correct answer is C

Given lines OA and OB inclined at angle θ, the line AB is gotten using cosine rule.

|AB|2=|OA|2+|OB|22|OA||OB|cosθ

|AB|2=42+522(4)(5)cos60

= 16+2520

|AB|2=21|AB|=21

The two particles are21mapart in 1 sec

In two seconds, the particles will be 221m apart.