[填空题]
A marble of mass m and radius r rolls alonge1.5nzw k 9zvk the lydq2b3*v49yads3l)m v)j7b6+d u+qjsfy dxbooped rough track of Fig. 8–58. What is the minimum value of the vertical height h that the marble must drop if it is to reach the higheddby)jl+j sa7f u+ b *sqyq6d4b )m9yvd3v3 2xst point of the loop without leaving the track? Assume $r\ll R$ and ignore frictional losses. h = R
