@JohnRennie Hi.Are u free

@Aladdin hi, yes

can u come to codeclub room

@JohnRennie Hi

@JohnRennie Hi! :)

@KevinN hi :-)

I've a got a question over here

If I was to illustrate a car moving in a circle:

And these are the different orientations when it's moving around:

It seems there must be a moment/torque on the car's tyres that is causing this rotation. Is this true?

I answered a question this some years ago. Let me see if I can find it.

@sammygerbil Long time no see?

@JohnRennie Hello

@pi-π hi :-)

@JohnRennie How do we find the direction of moment generated by these couples?

I don't know to be honest. I don't remember how to add couples - it's more engineering than physics. It probably wouldn't be hard to Google for how to add couples.

@JohnRennie On the previous answer link you gave. Are you, in other words, saying when a car makes a turn, you could break the force into two vector components? One directed towards the center of the rotation and the other as if it was to move straight? Just like this:

Yes

When the wheels are pointing in the direction of motion the force between the tyres and the road is straight on i.e. in the direction of travel (that's the force needed to overcome air resistance, friction, etc).

When you turn the wheels this produces a force normal to the direction of motion, and hence the wheels (and the car they are attached to) start to move sideways.

That wasn't actually my main question but it was a very interactive approach nonetheless. About 3 months ago I asked a similar question like this but it was of a different case, about spacecrafts, satellites, etc to be precise.

The question was like this : Now, if you look at how the plane (or anything) is orbiting, it seems as if it is rotating continously. This was the question that was stuck on my head. If the centripetal force acts on the centre of mass, what is causing this "rotation"? Meaning that, there must be some moment/torque applied. I really couldn't wrap my head around this.

That was the picture

You said " Yet, that is exactly what would happen."

and "you have to make the plane rotate at the same rate that it orbits."

"If you wanted the spacecraft to be moving like this" (picture above)

@JohnRennie Now moving to the car scenario. So when turning the front wheels, would this mean it would already create the rotation/torque?

I'm not sure what you are asking to be honest?

There is a torque on the car because the lateral force at the front wheels isn't in line with the centre of mass of the car.

So if a car was made with its wheels all along the line of the COM. Then turning the wheels would not turn the car?

I'd have to think about it. That would be a weird setup.

A very wierd one :)

@JohnRennie Right now, I'm trying to imagine if let's say whenever the front tires are turned, correspondingly the rear wheels would turn the same too.

So no matter how hard you try to rotate the car's body, you'll end up having the same orientation.

Here's a rough illustration I made:

@JohnRennie This would probably be the same case if the wheels were to be below the COM, but I'm not sure

In a car all four wheels don't turn.

Typically only the front wheels turn.

Yes :)

I was just trying to illustrate what would happen if all four wheels were turning

@JohnRennie I'll be around for the the next couple of hours, so ping me if you come up with something new about the "weird" car setup :)

I think when you said There is a torque on the car because the lateral force at the front wheels isn't in line with the centre of mass of the car. is conclusive enough.