sir. long is correct.. 打过球的或者有基本物理知识的都应该

http://en.wikipedia.org/wiki/Topspin Tennis Other than trajectory in air, top spin affects the bounce of the ball as shown. In tennis because of a net being in the middle of the court, using topspin will increase the player's consistency. Topspin also allows a player a greater margin of error. Because topspin brings the ball down toward the ground quicker, a player can hit the ball higher over the net, thus increasing the margin of error. This may help in lobbing an opponent that is waiting at the net, or playing directly to a player's feet. Hitting low to high as the player approaches the contact point will impart lift. Keeping the racquet face (the strings) slightly closed from perpendicular will impart the topspin to the ball that the player wants. However, balls that bounce lower due to greater force or backspin are much more difficult to return using a grip that confers topspin such as the semi-western and western grips, as the racket is angled too far downwards to 'lift' the ball back over the net. As such, topspin is more effectively used on slower, higher bouncing surfaces such as clay. Topspin is also far more difficult to impart on backhand strokes due to the physical limitations of an arm stretched across the body.

所有跟帖： 

• 研制发球机 -大号蚂蚁- ♂ (0 bytes) () 04/03/2013 postreply 09:09:21

• 我现在才知道纸上谈兵的厉害。 -edison11- ♂ (0 bytes) () 04/03/2013 postreply 09:25:29

• edison11,抱抱。不要哭了。这里真打球的不多。 -FanToo- ♂ (0 bytes) () 04/03/2013 postreply 11:45:59

• 俺的个娘，都上城头了。我勒个去。 -FanToo- ♂ (0 bytes) () 04/03/2013 postreply 11:48:10