Car problem homework

[Muniacal]

nearly school hols. but science teach has spolied it. For homewk I have to figger out why a car wi=th no power steerng acn be steered round a corner by a driver using just one fin=ger.. Why can he turn a heavy car without doing much hard work and gettng tired. Im clueless

Got my dad to tryu it and he could but it didnt help any


thanx fore any help.

[iridemymuni]

is it a slot car? you know the ones that run along a small track and you have a little controller to change its speed?

http://www.steelcityhobbies.com/images/Chicago%20Expo%202003/SlotCar2LG.jpg

[tomtrevor]

but those slot cars arent really that heavy so you aren't really turning a heavy car.

[iridemymuni]

but those slot cars arent really that heavy so you aren't really turning a heavy car.

heavy in relation to what?

[kington99]

I think the point here may be that it is genreally easier to turn the wheel at speed, to the extent that most luxury car manafactureres turn the power assist off over about 70mph on their cars. Power steering is much more useful for manouvering, when the steering is very heavy. This is because when you're stationary (or moving at low speeds) your effort is going in to twisting the tyre relative to the ground, which requires large force as the tyre has a large coefficient of friction because it's designed to grip the road. When travelling along you only have to turn the wheels a little relative to the ground before the car alters its direction so that you're travelling in the direction the wheels are pointing, and the force reduces to zero again.

It my also have something to do with the fact that at higher speeds turns tend to be less tight i.e. the freeway doesnt have sharp 90 degree turns like turning at the corner of a block does. If we imagine for instance turning in a carpark at 5 mph, and turning by the same amount in the same time on a major road, the turn on the major road will require the wheel to be turned much less because you're travelling a much larger distance in the same time due to the higher speed, so the turn is less severe.

I'm not sure how correct this stuff is, but I thought it would atleast give you a starting point.

[iridemymuni]

well i wouldnt say going down the highway you would call it a corwer. i would call it a bend.

a corner is a corner, a smooth bend in what you would find in a freeway.

thats what i think at least.

[tomtrevor]

heavy in relation to what?

in relation to an actual car.

[iridemymuni]

in relation to an actual car.

define actual car. a slot car is an actual car.

[tomtrevor]

an car that you drive, its not rocket science.

[iridemymuni]

you still drive a slot car.

you control the acceleration which is what you do in a normal car.

[kington99]

This isn't a semantics thread, obviously the original problem concerned a car capable of conveying people.

And incidently you control both the velocity and acceleration of a car.

[Hazmat]

My dad has a 92 swift with no power steering and i can drive it with 1 finger around corners no problems. It's not that hard once you get used to it. Now i do it everyday. :p :p

[iridemymuni]

My dad has a 92 swift with no power steering and i can drive it with 1 finger around corners no problems. It's not that hard once you get used to it. Now i do it everyday. :p :p


how heavy is it?

[Hazmat]

Do you mean the car or the steering??

[iridemymuni]

thats what im thinking. im not sure. do they mean heavy as in weight of the car or heavy as in it is hard to turn.

im sure you could turn it easily while your going(we had a 1970's leyland 6 tonne truck with no power steering, you could spin the wheel half way round the world before it would lock. the play in the wheel was about half a revolution soou could drive down the road and turn it 180 degrees and still go the same way it looked so cool. it was easy to turn while driving. but while going slow you really had to tug it with 2 hands.)

[kington99]

we had a 1970's leyland 6 tonne truck with no power steering, you could spin the wheel half way round the world before it would lock.

steering heaviness is of course a function of the steering geometry, the fact that you had to spin the wheel a long way to lock suggests it was very low geared, hence you didn't require power assistance.

[iridemymuni]

steering heaviness is of course a function of the steering geometry, the fact that you had to spin the wheel a long way to lock suggests it was very low geared, hence you didn't require power assistance.

only at speed. when going very slow you really had to get 2 hands on it and move your whole body

[tobbogonist]

i was going to post what kington99 said early on but only using normal peoples english but now i cannot be bothered because i have seen that he already did it.

[Hazmat]

Where my dad works we have Toyota Dyna 100-200 diesel. I sometimes work there if i need the extra $$$. Man they're fun to drive. Even the ones without power steering are fun. I can take off from lights in 2nd gear hahaha. The upside to having them is they're are cheap to fix becuase of them being toyotas. The down side is when the box is full and you're driving through harsh rain and some guy just presses the brakes hard. Luckily my dad told to keep my distance in the rain. So i've preety much avoid having prangs and stuff. It's all good:D :D

Oh and BTW my dads car is a 94 not 92 my bad. It weighs just under a tonne now and it has 41kw now instead of 39kw as it says here. It's not much but the fuel economy and take-off seems to have improved slightly. :D
http://www.redbookasiapacific.com/au/vehicle/specs.php?key=SUZU94BF

[Naomi]

OK, this is homework, for a 13 year old. So it is not going to need any of the real complexities of steering geometry etc. You can ignore all that and treat it as a simple mechanics problem.

I think the teacher is asking for you to look at two areas. Firstly he wants something on leverage and gearing which are relevant in determining how much force is needed, Secondly he is looking for a discussion of motion in a circle and in particular how much work is being done in maintaining that circular motion.

I suggest keep it simple and work around those two areas, expaining them and therefore saying why the driver does not have to work hard and Sir should be happy. Enough of a clue for you?



Nao

[monkeyman]

Come on Nao, what was that? You didn't answer his entire project for him, writing out explicit, step-by-step directions for every part of the problem (and don't forget telling him the right answer so he can check his work when he's done)! That wasn't very good help....:p

[kington99]

only at speed. when going very slow you really had to get 2 hands on it and move your whole body

Yes, but with it being a six tonne truck if it had normal 2 1/2 turn lock-to-lock you probably couldnt move it atall at low speeds.

Naomi, as usual you've expressed yourself far more clearly and concisely then I would ever find possible, i feel good that somone has expressed what i was trying to say, even if it wasn't me. What is your background in physics?

[iridemymuni]

dude Naomi is a teacher !!

at least i think she is. she helpd me with my maths assignment, thanks !!

[Naomi]

Yes, but with it being a six tonne truck if it had normal 2 1/2 turn lock-to-lock you probably couldnt move it atall at low speeds.

Naomi, as usual you've expressed yourself far more clearly and concisely then I would ever find possible, i feel good that somone has expressed what i was trying to say, even if it wasn't me. What is your background in physics?


Thank you KT99.

God, this feels almost like a confession.

I do some lecturing in both Maths & Physics to university students. A fairly recently acquired Ph.D. also goes some way towards helping with the odd 13 year old kid's physics homework. It is refreshing occasionally to be able to bring things back to ground level, and to ignore all the complexities I would usually have to get involved with.


Nao

[squirrel]

neat problem, I'm an engineer who's been driving manual steering cars and trucks for many years, and I don't know what the simple answer is!

although I will say that some of those older vehicles take more than a finger's force just to keep going straight on a straight road at speed

[yoopers]

neat problem, I'm an engineer who's been driving manual steering cars and trucks for many years, and I don't know what the simple answer is!

although I will say that some of those older vehicles take more than a finger's force just to keep going straight on a straight road at speed
I would imagine the steering wheel's moment arm could be increased to an extent where a finger turn would be easy. Is there a limit on the diameter of the steering wheel?

[squirrel]

getting new tires, replacing all the worn parts in the suspension and steering, and aligning it could probably accomplish the desired result.

[Joe2005]

getting new tires, replacing all the worn parts in the suspension and steering, and aligning it could probably accomplish the desired result.
WHAT that's cheating a self terning car! :p

I think yoopers is right. Adding onto that thought the stearing could be geared down also i.e. turn the wheel once and the tires move half the distance.

[squirrel]

For homewk I have to figger out why a car wi=th no power steerng acn be steered round a corner by a driver using just one fin=ger.. Why can he turn a heavy car without doing much hard work and gettng tired.

I think the short answer is "because the tires are rolling"

[yoopers]

WHAT that's cheating a self terning car! :p

I think yoopers is right. Adding onto that thought the stearing could be geared down also i.e. turn the wheel once and the tires move half the distance.
Where's Harper's Blue Streak when you need it?

[johnfoss]

Possible answers:

1. The driver is Sean Connery's character from the movie The Presidio. In that movie he beats up a big biker-looking bar thug with just his left thumb (his weaker one).

2. Face the car uphill, and the steering will get much easier.

3. Use one of the new Lexus (Infinity? Acura?) cars that can park itself, hands free. Uh, I guess that one doesn't count because the car undoubtedly has power-assist steering...

4. Do finger exercises. I think the average car is not too hard to steer when it's moving at 5mph or faster.

I would lean toward #2 for my main answer.

[skianduniaddict]

in nascar they ahve banked turns

[Muniacal]

OK, this is homework, for a 13 year old. So it is not going to need any of the real complexities of steering geometry etc. You can ignore all that and treat it as a simple mechanics problem.

I think the teacher is asking for you to look at two areas. Firstly he wants something on leverage and gearing which are relevant in determining how much force is needed, Secondly he is looking for a discussion of motion in a circle and in particular how much work is being done in maintaining that circular motion.

I suggest keep it simple and work around those two areas, expaining them and therefore saying why the driver does not have to work hard and Sir should be happy. Enough of a clue for you?



Nao




Thanx naomi that fits well with the stuff we have been workin on the last few weeks. I done some reading and i thoink I can see what to do now.
So in thoery he does no work at all I guess? Is that right?

lots of other intresting stuff in the posts but most of it not to helpfull for my problem. thanx to evryone.


Muniacal

[ivan]

Thanx naomi that fits well with the stuff we have been workin on the last few weeks. I done some reading and i thoink I can see what to do now.
So in thoery he does no work at all I guess? Is that right?

lots of other intresting stuff in the posts but most of it not to helpfull for my problem. thanx to evryone.


Muniacal
Work done = force x distance.
He moves the steering wheel, but the force which he has to apply to move it is less. Therefore, work done is less as well. But it's not zero. He still has to move the wheel to turn.

[Naomi]

Work done = force x distance.
He moves the steering wheel, but the force which he has to apply to move it is less. Therefore, work done is less as well. But it's not zero. He still has to move the wheel to turn.


When initially turning the wheel, yes, work is done. Once turned through a specific angle, then if you maintain that constant angle, and therefore the radius of the driven circle, no more work will be done. You could drive, at constant speed, on a flat surface, with a weight hanging on one side of the steering wheel, arms folded and not touching the wheel. Once in that steady state, there is zero distance in that W=F*D equation, so the weight will then be doing no work, but the car still turns. The force is still there, but it is not a working force.
I think the teacher will be happy with the steady state situation.


Nao