標題: 有關work done的問題 [打印本頁] 作者: ting 時間: 14/6/2007 08:30 PM 標題: 有關work done的問題 A constant force of water is used to raise a box of 1 kg vertically from the ground over 1.5 m. The force has done 30 J of work on the box.
What is the acceleration of the box?
請問work done有否已考慮了weight 計acceleration果陣洗唔減個weight?作者: sapphire 時間: 14/6/2007 10:20 PM P.E. gained by the block=mgh=15J net energy W gained by the block=30-15=15J
W=Fs F=10N
F=ma a=10 ms^-2
Since 30J is done by the constant force only, it is required to consider the amount of the P.E. gained by the block. Also, in this case, F is the resultant force of the block. It is no need to consider the weight of the block when calculating the acceleration.