v1^2=2gh1v2^2=2gh2(1/2mv1^2)/(1/2mv2^2)=v1^2/v2^2=h1/h2=1/41m和4m的动能之比是1/4v1=gt1v2=gt2(1/2mv1^2)/(1/2mv2^2)=v1^2/v2^2=(t1/t2)^2=(1/4)^2=1/161s和4s时的动能之比是1/16