题目

大象的质量是4800kg，每只脚底的面积是600cm2。取g=10N/kg，如图12所示，当大象四足站立时，求：⑴大象的重力；⑵大象对地面的压力；⑶大象对地面的压强。 答案：(1)4.8x104N    (2) 4.8x104N     (3)2x105PaThe boy was very sick, but he managed to ______.A．pull offB．pull outC．pull throughD．pull up