a boy stands on the edge of a cliff of height 60m.he throwws a stone upward so that its distance ,ha boy stands on the edge of a cliff of height 60m.he throwws a stone upward so that its distance ,h m,above the cliff top is given by h=20t-5t^(b)calcu

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a boy stands on the edge of a cliff of height 60m.he throwws a stone upward so that its distance ,ha boy stands on the edge of a cliff of height 60m.he throwws a stone upward so that its distance ,h m,above the cliff top is given by h=20t-5t^(b)calcu

a boy stands on the edge of a cliff of height 60m.he throwws a stone upward so that its distance ,ha boy stands on the edge of a cliff of height 60m.he throwws a stone upward so that its distance ,h m,above the cliff top is given by h=20t-5t^(b)calcu
a boy stands on the edge of a cliff of height 60m.he throwws a stone upward so that its distance ,h
a boy stands on the edge of a cliff of height 60m.he throwws a stone upward so that its distance ,h m,above the cliff top is given by h=20t-5t^
(b)calculate the time which elapses before the stone hits the beach
(c)calculate the speed with which the stone hits the beach

a boy stands on the edge of a cliff of height 60m.he throwws a stone upward so that its distance ,ha boy stands on the edge of a cliff of height 60m.he throwws a stone upward so that its distance ,h m,above the cliff top is given by h=20t-5t^(b)calcu
（1）20t-5t^2=-60,t=6 seconds
(2)based on the equation of mechanic energy,
the velocity v0=20m/s,so
m*g*h=0.5*m*(vt^2-v0^2)
that is
10*60=0.5*(vt^2-20^2)
vt=40meters per second

time is 6 s

One of ( ) up and answers the question.A.the boys stands B.boys stands C.the boy standsD.boy stand a boy stands on the edge of a cliff of height 60m.he throwws a stone upward so that its distance ,ha boy stands on the edge of a cliff of height 60m.he throwws a stone upward so that its distance ,h m,above the cliff top is given by h=20t-5t^(b)calcu The big star on our national flag___the Party.A.stands up B.stands for C.instead of D.mean The girl stands (填A,B,C)the bookshelf.A.on B.in C.beside The boy is sitting in the garden in front of which stands a tree这句子的原序 The children are going to play a game.They are standing in two rows.The girls stands in the firstrow.The boys stand in the second row.Mary stands in the middle.Betty stands her right handside.Han Meimei stands on Mary's left handside.Gina stands on t the boy is sitting on a chair 10.The boy can add double________.A.number B.finger C.figure D.figures12.We play volleyball on the _________ of a lake.A.edge B.side C.site D.size13.The machine stands on a wooden ________.A.bottle B.bottom C.base D.basis5.Help me with these bags,___ The boy is my brother.The boy stands in front of the house.改成定语从句 a boy stands on the edge of a cliff of height 60m.he throwws a stone upward so that its distance ,h m,above the cliff top is given by h=20t-5t^(b)calculate the time which elapses before the stone hits the beach(c)calculate the speed with which the st There used to be a house_____ on the top of the mountain.A.standing B.stands C.stood D.stand 英译中2句This gird in the row stands for betting on a particular horse which runs at the first place.This gird in the column stands for betting on a particular horse which runs at the second place. what is on () dask A,boy is .B,boy.C,the boy.D,the boy is .怎么填 The house which stands on the hill is mine. some of the new products will be on display at our stands.求翻译！our stands. At the school gate stands a blackboard,__reads Welcome Back.A.which B.that C.on which D.where There is a boy in the（ ） on the wall the boy ＿＿ at the bus stop and＿＿his mother.A stand,waits B,stppd,waited for C,stands,wait D,is,waiting