From the ground, particle A is projected vertically upward with 30 m s⁻¹. Simultaneously, particle B is projected vertically downward with 20 m s⁻¹ from a point 100 m above the ground. Taking g=10 m s⁻², they collide at a height:
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Question

From the ground, particle A is projected vertically upward with 30 m s⁻¹. Simultaneously, particle B is projected vertically downward with 20 m s⁻¹ from a point 100 m above the ground. Taking g=10 m s⁻², they collide at a height:

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G1 Physics · Accepted Answer

Both particles have the same downward acceleration, so relative acceleration is zero. Initial separation = 100 m. Closing speed = 30 + 20 = 50 m s⁻¹. Collision time: t = 100/50 = 2 s. Height of A then: y = 30(2) − 5(2²) = 40 m.