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Old Mar 14th 2011, 03:49 AM   #1
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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
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Old Mar 14th 2011, 06:53 AM   #2
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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.
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Old Mar 15th 2011, 02:50 AM   #3
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Im still getting confused with part (b).

So the weight = 4000 cos 37 ?
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Old Mar 15th 2011, 03:36 AM   #4
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The weight component is given by mg sinA (where A is the angle of the slope)

Weight component = 250 * 9.8 * sin(37)

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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?
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Old Mar 15th 2011, 03:42 AM   #5
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Thanks mate

Youve been a great help.
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