问题
选择题
A firm from New Zealand has revealed a set of robotic legs which they claim will soon
allow _______ wheel chair - bound people to walk again.[ ]
A. originally
B. previously
C. properly
D. primarily
答案
答案：B
="16" cm,
=" 48" cm，摆长为64 cm（可视为不变），摆角小于5°，则该沙摆的周期为______s，木板的加速度大小约为______ m/s2(g取9．8m/s2)