Particle A moves with constant speed 10 m s⁻¹. Particle B moves with an unknown constant velocity. At an instant the line joining A and B makes 30° with A's velocity. Find the minimum possible speed of B if they are to collide later.

Question

G1 Physics · Accepted Answer

For collision, relative velocity must be directed along the line joining the particles. The minimum magnitude of B's velocity occurs when B supplies only the component of A's velocity perpendicular to the line AB. That component is 10sin30°=5 m s⁻¹. Option A.