[填空题]
A ball is dropped from;7z dentbc d4avt6)nz)hkn 0c jem0:8 a height of 1.uq 0.j5xdpd 1 yi0bx0ly+v.kgis: z4o 50 m and rebounds to a height of 1.20 m. Approximately how many rebounds ul 0x.vyqks5zy1g0p4+ji0bd.id: x o will the ball make before losing 90% of its energy?
