Physics Help Forum Work and Energy

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 Mar 14th 2011, 03:49 AM #1 Junior Member   Join Date: Feb 2011 Posts: 18 Work and Energy Hi. A motorcycle (mass = 250) is travelling at a steady speed of 20 m/s. THe forc of air resistance acting on the cycle and the rider is 200N. Find the power necessary to sustain this speed if (a) the road is level, and (b) if the road is sloping 37 degrees upwards with respect to the horizontal. Please help. I dont know where to start <3
 Mar 14th 2011, 06:53 AM #2 Physics Team     Join Date: Jun 2010 Location: Mauritius Posts: 609 It's simple; the application of F = ma and components. a) If the road is level, then the Engine force = Resistive force F_d = F_r F_d = ? Then, Power = Engine Force x Velocity (b) Break down the force due to gravity to get the weight component of the motorcycle. Weight component + Resistance = Engine force Engine force = ? Then, use P = Fv again. __________________ Jerry (Got my results!) It is easier to protect your feet with slippers than to cover the earth with carpet. No one can go back and change a bad beginning; but anyone can start now and create a successful ending. If a problem can be solved, no need to worry about it. If it cannot be solved what is the use of worrying?
 Mar 15th 2011, 02:50 AM #3 Junior Member   Join Date: Feb 2011 Posts: 18 Im still getting confused with part (b). So the weight = 4000 cos 37 ?
 Mar 15th 2011, 03:36 AM #4 Physics Team     Join Date: Jun 2010 Location: Mauritius Posts: 609 The weight component is given by mg sinA (where A is the angle of the slope) Weight component = 250 * 9.8 * sin(37) __________________ Jerry (Got my results!) It is easier to protect your feet with slippers than to cover the earth with carpet. No one can go back and change a bad beginning; but anyone can start now and create a successful ending. If a problem can be solved, no need to worry about it. If it cannot be solved what is the use of worrying?
 Mar 15th 2011, 03:42 AM #5 Junior Member   Join Date: Feb 2011 Posts: 18 Thanks mate Youve been a great help.

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