The science bit

Sir isaac newton figured it all out, and we've been playing by his rules ever since. Here's why lightweight is better

4y ago

OK firstly a warning - this is just the basics, but it will still take you a good 5 or 10 minutes to get through, and you could probably use that time more wisely but if you're really intrigued about the science behind Superleggera, read on.

I'm not a scientist. I did ok in physics and maths and the mechanics of movement were enough to keep me intrigued. I learned that a very clever man called Sir Isaac Newton figured some stuff out, and managed to narrow down what he knew into three fundamental laws. These three laws formed the basics of mechanics, and the very essence of what controls where we're going and how quickly we get there or change direction.

Specifically in this post, we're concerned with Newton's second law: F=ma

Fundamentally what he figured out was that if a resultant force (F) is applied to a mass (m) then there will be acceleration (a). Your physics teacher can tell you a lot more than you'll read here, but I'll keep it fairly brief and tell you why this is as exciting as big V12s and bodykits. I'll also be speaking British English here, so don't try to correct me if your country uses different spellings and currencies...

If we go back to high school we know that we need to keep equations balanced. If I said 2 apples cost £1, then you know 4 apples cost £2. That's because you've doubled both sides of the equation. 2 x apple = 1 x pound. Double that gives 4 x apple = 2 x pound.

Indeed, if we divided both sides by the same amount, again the equation remains balanced and therefore true, i.e. (2 x apple) /2 = (1 x pound) /2

so 1 apple = £0.50

Makes sense, right? And so, let's relate that back to Newton's second law which we know to be F=ma. What Newton is saying there is that the value of the force (measured in, predictably, 'Newtons') EQUALS the sum of multiplying the mass (in kilograms) by the acceleration (in metres per second per second, or "metres per second squared").

So, Force = mass x acceleration.

As we said before, if you apply the same adjustment to each side of an equation, it stays true, so to see how acceleration relates to the others, we can divide both sides of Newton's equation by 'mass' - giving

Force/mass = acceleration

Now, acceleration is the bit we're interested in for many reasons. In the simplest sense, the term is used on a daily basis to describe an increase in speed. However, this is not the purest meaning of the word. It's not simply an increase in speed, it is a change in velocity. That's right, acceleration actually means change in velocity. Now, I know you're thinking that an increase in speed IS a change in velocity, and you're right; but there are lots of other ways to consider a change in velocity which are equally as valid a description of 'acceleration'.

'Speed', you see, is how much ground you've covered in what time. A GP car zooms around 200 miles of racetrack in about an hour and a half, and so has an average speed of around 200/1.5 = 133.33 miles per hour. However, if they end up where they started - which they do (roughly, depending on grid position, yes I am a pedant) - then their total 'displacement' (i.e. how far the moved from the start) is zero. And it took them an hour and a half. So their average velocity for the race, which is a consideration of displacement, is actually zero. Yes, 0 metres per second. They ended where they started.

As well as velocity being a consideration of the object's displacement, it also considers the direction of its movement. This is where stuff gets very interesting, and why mass is so critical. To change something's direction, therefore, you have to change the velocity. Now, remember velocity is not speed - the object can be travelling north at a 'speed' of, say, 50mph; and then to make it turn east (even if it stays at a speed of 50mph) you are changing its velocity, because although the rate of displacement at any point either side of the direction-change is unchanged, the direction itself has been. And so, if you've changed the velocity at the time, it has accelerated in the purest sense.

To summarise - to go from 50mph northbound to 50mph eastbound, you have changed velocity - i.e. you have accelerated.

Now, remember we said acceleration = Force/mass? It seems a while ago we said that, but we did. Well, in order to apply that acceleration to anything that has a mass (i.e. 'm' is not zero) then we must apply a force.

That makes sense, if something is heading happily in one direction and no force is applied like friction, gravity etc, then it won't change (in fact that's Newton's first law...), and so whatever shoved it to change direction was the 'F' in our equation.

The equation also reveals that for a certain force, you can therefore get a higher amount of acceleration if the mass is lower. Remember, acceleration = Force/mass, so you want mass to be small so you're not dividing your force by as much, and therefore giving more acceleration.

Again, in simple straight line terms that makes sense. If you use all your might to pull a trailer full of bricks, you are 'F', the mass of the trailer is 'm' and the amount of acceleration you get is 'a'. So, making 'm' smaller (e.g. taking half the bricks out) mean you can accelerate that trailer easier even though you are not now having to use any more force to do so.

But it also makes it easier to stop the trailer once it's moving - because if it weighs less, you need less force to stop it - so even decreasing the velocity needs a force - hence why we said acceleration is a 'change' in velocity, not an 'increase'.

So that means acceleration (speeding up) and deceleration (slowing down) have been made easier with a lower mass, because slowing down needs a force too - so in car terms, the lighter you are, the more effectively you can reduce your speed with your brakes' combined force.

Stopping is easier. Getting going is easier. And cornering? Well surprise surprise that works too - as I said, velocity has a direction as well as a magnitude, so if you want to change direction you need a lower mass if you want to achieve a quicker change of direction with the same force.

Cars can increase the force instead, sure, by having more grip in corners through better tyres, downforce, clever suspension set-up etc. But, if you've already maximised those, the reduction in mass simply makes cornering quicker. Which is great.

In summary a reduction in mass covers all bases.

To accelerate faster, you could have more power, or less mass.

To brake later, you could have more powerful braking, or less mass.

To corner more quickly you could increase grip, or have less mass.

Therefore having less mass - i.e. a lower weight (weight is just mass multiplied by gravity, which on earth is fairly consistent across the surface) - helps you speed up, slow down, and go round a corner.

If you wanted all those things without lowering mass, you'd need to increase power, uprate your brakes, and fit bigger or grippier tyres, better suspension etc. and all those things could actually add more weight than you had already. Which seems to me like doing it the hard way.

So there you go, the basic of why mass should be rejected. Super-Physicists out there will know I've simplified things to keep them relatable, but short of popping into outer space to keep everything ideal you'll have to make do. In future posts on here I'll look at how companies are doing that with lightweight materials, clever manufacturing, and how to best use the mass you need to make sure it's in the right place on your vehicle - but that's a whole new load of science... but all still relates back to what Sir Isaac Newton wrote down. Who's Adrian Newey, anyway?

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Comments (1)

  • Well written. Should be shared with high school physics teachers.

      4 years ago