[填空题]
While practising, a table tennis player hits ag2kl5i: 4urjt zdf1 xqbliqtkno:, o3/r 2.fqz842il ball of mass $2.8\,g$ that collides with the floor and then bounces back from the wall. The speed of the ball just before reaching the floor is $8.0\,ms^{−1}$. The ball leaves the floor with an angle of $65^{\circ}C$ to the floor as shown.
1. Due to the collision with the floor, the ball losses 30% of its initial kinetic energy. Calculate the leaving speed of the ball from the floor. $v$ = $ms^{-1}$
2. The ball strikes the wall just as it reaches the highest point of its motion. Determine the horizontal distance between the bounce point and the wall. $d$ = $m$
3.The ball collides elastically with the wall, with the time of contact during the collision is $0.040\,s$. Calculate the average horizontal force exerted by the wall on the ball during the collision. $F_{ave}$ = $N$
