[填空题]
The motion of an object released from a high plr )knwzfy1y:5ew .lt7ace in a vacuum is observe jsztx0+( qxh+r 8m,gbd. The variation of its velocity with ,g(hx0zb m+q jxsr +8ttime is recorded and the following graph is obtained.
1.Discuss the role that observations play in the development of scientific understanding.
2.Other than velocity and time, Can both displacement and acceleration be obtained from the graph?
3.
(1) The height of the release point is $70\,m$. Calculate the speed $v_1$ of the object just before the contact with the ground. $v_1$ = $ms^{-1}$
(2)The object rebounds from the ground with a speed $v_2$ of $17\,ms^{−1}$. The mass of the object is $8.0\,kg$ and the contact time during the rebound is $0.50\,s$. Calculate the average force acting on the object from the ground. $F$ = $N$
