1.
圖片參考：http://imgcld.yimg.com/8/n/HA04937267/o/701201200004413873421970.jpg
2.A similar question:
A boy kicked a ball of 1.2kg on level grassland. The ball rolled for 20m before it stopped. What was the resistance? Express it in terms of the initial speed of the ball u.
A.0.01u^2
B.0.02u^2
C.0.03u^2
D.0.04u^2
ans:
圖片參考：http://imgcld.yimg.com/8/n/HA04937267/o/701201200004413873421971.jpg
我想問點解resistance係net force?但係個boy exert左force落個ball到喎,why net force唔係resistance-boy exerted 既force?
3.
圖片參考：http://imgcld.yimg.com/8/n/HA04937267/o/701201200004413873421982.jpg
更新1:
可能圖太細,下面有放大版 Q1: http://i615.photobucket.com/albums/tt234/chandaiman199111/1bacf1fe.jpg Q2: http://i615.photobucket.com/albums/tt234/chandaiman199111/2.jpg
更新2:
4. http://i615.photobucket.com/albums/tt234/chandaiman199111/008.jpg 因為我未學正比同反比,所以唔明: 1.acceleration directly proportional to force (constant mass) 2.acceleration inversely proportional to mass (constant force) 1同2我明,但我唔知點解combine their relation會得出 acceleration directly proportional to force/mass