Help with mechanics question please (1 Viewer)

J-Wang

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I'm sure there's a simple way of doing this, but i just cant see what it is. could someone please do this question with steps that i can follow?
thanks

The question is:

The combined air and road resistance of a car in motion is proportional to v^2, where v is its speed. When the entire engine is disengaged the car moves down an incline making an angle of inverse sin 1/30 [sin^-1(1/30)] with the horizontal, with a velocity pf 30m/s. Find the force required to drive the car up the incline with a steady speed of 24m/s, given that the mass of the car is 1200kg and g=10m/s^2

Thanks, and good luck
 

IamBread

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When the car is going down the hill, the forces acting upon it are


Now that we know k, we have everything we need to find the force.

The force acting on the car when it is moving up the hill is


This is the force acting on it, so the force needed to overcome it is
 
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J-Wang

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When the car is going down the hill, the forces acting upon it are


Now that we know k, we have everything we need to find the force.

The force acting on the car when it is moving up the hill is


This is the force acting on it, so the force needed to overcome it is
the answer is 656N :p
 

J-Wang

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I know what I did wrong....

fixed it.
thanks mate. would it be possible to upload a diagram of how u did all that? just so it can help visualise. i understand the maths, just visually the diagrams help lol
 

IamBread

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thanks mate. would it be possible to upload a diagram of how u did all that? just so it can help visualise. i understand the maths, just visually the diagrams help lol
I didn't use a diagram lol, that's where the error came in :p
But I'll draw something up.
 

qwerty44

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Mechanics looks hard, though everyone says its not compared to others. Can't wait to start MX2.
 

IamBread

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It's not hard, it is fun though, was probably my favourite topic in MX2! When you first look at it, it looks hard, but when you do it it's not really :p
 

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