A50Kgdiverstepsoffa10mhighdivingboardanddropsstraightdownintothewater.Ifthedivercomestorest5mbelowthesurfaceofthewater,determinetheaverageresistanceforceexertedonthediverbythewater.最好带些讲解的.

Question

A 50Kg diver steps off a 10m high diving board and drops straight down into the water.If the diver comes to rest 5m below the surface of the water,determine the average resistance force exerted on the diver by the water.
最好带些讲解的.

Answer 1

50Kg的人从10m高处掉下摔进水中.如果他最深沉在水下5m,求水的平均阻力.
全过程动能定理,
mgh-W=0-0=0
m=50
g=10
h=10+5=15
W=mgh=1500*5
而平均阻力f乘以阻力方向的位移是W
所以,f=W/H=1500
又阻力做负功,所以f=-1500