题目内容
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听力原文：The most common type of child abuse you know is beating with the hands or with an
听力原文： The most common type of child abuse you know is beating with the hands or with an instrument usually a cane in some places. Nearly a third of the abused children we see are in the age group between six and ten, and about sixty-five percent of them are boys. This is the age group when children are first to expect to study hard and parents have great expectations of their progresses in school.
Boys of course attract more abuse such as beating because once again parental expectations are high, and boys tend to be more energetic and difficult to control than girls. Most experts seem to agree that the child abuse is caused by a combination of social and psychological factors. Families who beat their children are not particularly different from other people.
The only difference that exists between them is that they lack skills in the establishing good relationships with their children. These families too, generally speaking, have other problems such as marriage problems or financial problems. Some parents are hurting their children because they strongly believe in the use of traditional discipline methods. But many of them have emotional problems. They are often the victims of violence themselves. Sometimes they even bear an unreasonable hatred for a child because they believe that the child has brought the thmily bad luck.
According to the passage, when are children first expected to study hard？
A．Before 6 years of age.
B．Between 6 and 10.
C．After l0 years of age.
D．After 12 years of age.
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is 200 mb for strong interaction reactions, like in the reaction
. Please estimate the order of magnitude of the cross section of the reaction:
which is dictated by the weak interaction. The incoming and outgoing energies are assumed to be same as those in the strong interaction case.
, the transition matrix element is written as
. please give proof for the momentum and energy conservations at vertices. As showin in the figure, the momenta and positions are labelled.
This is actually related to the photon propagator
,with
while for static case,
. Please prove the relation
.
, Please prove: the corresponding potential V is given as
,(hint: the meson's equation of motion is given as
, then take the static case). Note that there would be a minus sign for V(r), but it doesn't matter.
