词组及地道用法：
1、date back to
▶Our present ideas about the motion of bodies date back to Galileo and Newton.
延伸
▶ ...-A perpetual struggle to discover how the University works that goes back to the earliest civilizations.
2、pure thought
▶...one could work out all the laws that govern the universe by pure thought.
自己造句：▶It's impossible to mediate the dilemma by pure thought.
3、lead weight 吊锤
▶If one drops two bodies that don't have much resistance,such as two lead weights,...
4、be proportional to
proportional properly related in size or degree or other measurable characteristics; usually followed by `to'
▶This states that a body will accelerate,or change its speed,at a rate that is proportional to the force.
5、have something doubled
▶Thus the force between two bodies would be twice as strong if one of the bodies(say, body A)had its mass doubled.
6、have+次数+something
▶One of the bodies had twice the mass,and the other had three times the mass..
7、for instance
▶For instance,one playing Ping-Pang on the train,...
8、accord with
▶...it didn't accord with his idea of an absolute God.
9、given和provided
given：介词，其后只能跟名词
▶Given his age,he did it quite well.
provided:连词或形容词，形容词意为“提供的”
▶...,provided they used a good clock.
▶Please put your litter in the bin provided.
▶To get these features working you first have to install the software provided.
