# Homework Help: Friction Question

1. Sep 3, 2007

### balogun

1. The problem statement, all variables and given/known data
I have a friction question wanting me to find the largest angle of slope a car can drive up at constant speed
if it has
a front wheel drive
b rear wheel drive
c four wheel drive

The real question is in the microsoft word file attached.

2. Relevant equations[/b
tan(teta)=F/N=co-efficient of friction

3. The attempt at a solution
I managed to do the four wheel drive question

tan(teta)=0.40
teta=6.84.
Could not do the rear wheel and front wheel questions.

Help is appreciated.
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

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2. Sep 3, 2007

### balogun

Sorry wrong file

Sorry i posted the wrong file the right one is here.

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3. Sep 3, 2007

### balogun

Another question

I have got another question.I have tried to do it but no matter what free body diagram I do cant seem to get anwser.

Question attached to file.

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4. Sep 3, 2007

### PhanthomJay

You meant to say tan theta =.12, not .40 for the 4 wheel drive case, didn't you? The answer is correct, although you did not show your work, so I assume you just used
u =tan theta for simple objects in uniform motion? That works here for the 4WD case due to symmetry, but in general, you must sum torques to solve for the normal force at each axle, and note that the traction provided by friction acts on the drive wheels only. Would you expect the angle to be less or more or the same, for the 2WD cases? Try summing torques about the contact point of one of the tires to determine the normal force on the other tire.

5. Sep 3, 2007

### kaisxuans

erm..im no professional in this topic but maybe you can give us some of you attempt to the questions first?

6. Sep 4, 2007

### PhanthomJay

Show or describe what you have for a FBD. Have you considered also that the tension in a cable wrapped around an ideal pulley is the same on both sides of the pulley?