total work=friction+ PEgained= 200j+500*2 j= 1200j
efficiency=workout/workin= 1000/1200
effort*distance=workin
effort=1200/ lengthofPlank I am wondering if your 4 cm should be 4 m.
A rough 4cm long plank is used road an inclined plane to raise a 500N bag up to the floor of a long lorry 2m high. 200j of work is done against friction between the bag and the plank.calculate (a) the total work done by effort (b) the efficiency of the inclined plane (c) the effort needed to pull the bag up the plane.
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