砰

Left stone radical (Kangxi #112) - the indexing radical, depicting a rocky outcrop under a cliff overhang. Anchors 砰 in the impact family: the heavy thud of stone striking is the sound the character imitates (a bang, a crash, a slam - 砰的一声 with a bang). Same radical groups 碎 (shatter), 砸 (smash), 砍 (chop), 破 (break).

Right phonetic 平 (píng) - supplies the sound directly without major shift. Same phonetic in 评 (píng review), 苹 (píng apple), 萍 (píng duckweed), 坪 (píng level ground). Pure phonetic here - no flatness in the bang sound. Recognising 平 on the right cues a píng reading.