unit8workandpower市公开课一等奖省赛课微课金奖课件.pptx

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,Unit 8 General Science,1/14,Work and Power,功和功率,2/14,*,功表示力和受力物体在力作用方向上发生位移乘积。,*功率表示力做功快慢程度。,W=F*S,P=,3/14,Fast reading,Read the text quickly and answer the following questions.,1.What is the definition of“,work,”?,2.How do you calculate the amount of work done?,3.What is the definition of 1,joule,?,4.What is the definition of“,power,”?,5.What is the definition of 1,watt,?,4/14,Work is done when a force causes an object to move or prevents it from moving.,the definition of“work”:,5/14,Equation:W=F*S,Work done=force,X,distance moved in the direction of the force,Work done equals force times distance moved in the direction of the force.,6/14,Example,An athlete applies a force of newtons to move up the weights to the height of 2 meters.How much work has the athlete done?,N,2m,Work done,=N X,2m,=4000J,7/14,1 joule,If a force of 1 N causes an object to move 1 meter,then 1J of work has been done.,1N,1m,8/14,The definition of“power”,Power is a measure of how rapidly work is being done.,Power=,9/14,1watt,If a person or a machine is doing 1J of work each second,the power rating is 1 W.,10/14,Example,Go on looking at the athlete,if the work takes the athlete 0.5second to lift the weights above his head,what is the power of the athlete?,Power=,=8000Wor 8Kw,11/14,Sum up,Work ;work done;1 Joule;power;1Watt.,Work done=N X 2m=4000J,Power=4000J 0.5s=8000w or 8kw,12/14,Homework,The lawnmower move needs 80 newtons,its engine can apply 50 newtons.A lady pushed the lawnmower along a straights line for 40 meters.How much work has the lady done?,13/14,goodbye,14/14,