114 votes

Why do cars have mirrors for rear view rather than cameras?

This is another case of fancy new (SHINY!!!) technology being A Bad Idea(TM) . When you're driving, your eyes are focussed roughly at infinity, i.e. looking at objects more than 5 m away. When you ...
Carl Witthoft's user avatar
61 votes

Why do cars have mirrors for rear view rather than cameras?

We still use mirrors because: A mirror is cheap, simple, passive technology that works. Pretty much the only failure mode is it breaking on impact. (Though I have had a center rearview mirror fall ...
Adrian McCarthy's user avatar
44 votes
Accepted

Why are engine blocks so robust apart from containing high pressure?

If you consider only the static forces then indeed the thickness might seem over-engineered. However, engine blocks are not statically loaded. They operate in the range of a few hundred to a few ...
NMech's user avatar
  • 24.3k
43 votes

Why are bulldozers so slow?

I wonder why can't we engineer.. We CAN engineer a vehicle which is both fast, and has a lot of torque. (E.g. a tank, as you mentioned yourself) The reason why we don't do this for a bulldozer (I.e. &...
Chris_abc's user avatar
  • 759
39 votes
Accepted

Why do heavy trucks use air brakes?

Biggest advantage is that when connecting to trailers, there are no bleeding issues. Imagine having to connect hydraulic pipes and remove the air bubbles... As for the amount of air - the compressor ...
Solar Mike's user avatar
  • 15.6k
32 votes

Why do cars have mirrors for rear view rather than cameras?

The industry is already going down that path for the exact reasons you mentioned. There is an article that provides information about that. In summary the main reasons why we don't have it yet are ...
idkfa's user avatar
  • 1,734
26 votes

Why are bulldozers so slow?

From memory, but pretty much realistic: a tank will use e.g. 1000 liters of diesel fuel just to move 100 km and will probably require a track maintenance afterwards. A truck with the same tank on its ...
fraxinus's user avatar
  • 499
22 votes

Why do cars have mirrors for rear view rather than cameras?

Digital camera systems with LCD screens impose latency of at least a frame on the images. Fine for slow moving parking cameras, maybe a problem at speed. An object moving at 60mph shown through a ...
pjc50's user avatar
  • 339
17 votes

Copper is more conductive, so why use lead battery terminals?

Yes, copper is more conductive than lead, but that is not necessarily the primary criterion for selecting the connector material. For car batteries, making sure there's a good connection between the ...
Dave Tweed's user avatar
  • 6,874
15 votes

Is there a reason (in terms of the physics involved) why it is better to push start a car in 2nd gear rather than 1st?

It depends on the car. If it's a big displacement high performance engine, then you may not be able to get the rear wheels to turn unless you're in the highest gear. If it's got an itty bitty engine,...
TimWescott's user avatar
  • 2,522
15 votes

Why are engine blocks so robust apart from containing high pressure?

You need to consider that the complete engine block has to withstand the reciprocating forces generated by each of the pistons and con rods moving as well as the rotational forces from the rotating ...
Solar Mike's user avatar
  • 15.6k
15 votes

Why do heavy trucks use air brakes?

Several characteristics led to the adoption of air brakes. The primary one is reliability. A leak on a hydraulic brake system means the brakes don't work. A leak on air brake system means the ...
Tiger Guy's user avatar
  • 6,813
12 votes
Accepted

Why wont Petrol engine run on Acetylene?

There are certainly a few reasons why acetylene is not a very practical fuel for an IC engine. Perhaps the most important is that it is inherently unstable and tends to explode under pressure, this ...
Chris Johns's user avatar
  • 15.2k
12 votes

What is the purpose of grid-like details on engine blocks?

This pattern is to provide sufficient strength while minimising the mass of the block. These "webs" are designed to prevent any vibration, if the block wall was made thin and the full length and ...
Solar Mike's user avatar
  • 15.6k
12 votes

Why are engine blocks so robust apart from containing high pressure?

The vibration, loading, and fatigue aspects have already been addressed, but a wide range of operating temperatures is another factor. A typical consumer engine can be deployed in anything from say -...
brichins's user avatar
  • 221
10 votes

Why do cars have mirrors for rear view rather than cameras?

Cameras are used as rear-view mirrors, simply not in mainstream passenger cars. For example, here's how rear-view is done in tramways: Aside from improved wind resistance which you mentioned, cameras ...
Dmitry Grigoryev's user avatar
9 votes

Copper is more conductive, so why use lead battery terminals?

A lead-acid battery has only lead and acid. If copper was used for the terminal posts galvanic corrosion would eat them. It is better to keep the same metal for the cell plates and the terminals. Also ...
ronald glen's user avatar
9 votes
Accepted

Is it true that four-wheel drive is less efficient and if so, why?

Simply put, power transmission is not free. Every time you have some energy over here, and you want to move it to over there, you are going to lose some of it in the process. In this case, if your ...
Daniel K's user avatar
  • 2,646
9 votes

Why do heavy trucks use air brakes?

"Power" brakes, like the ones you have in your car, use air pressure to assist your pedal effort. In passenger cars the air pressure is actually negative: it relies on intake manifold vacuum....
stretch's user avatar
  • 231
9 votes

When a car with an open differential turns, why does the inner wheel slow down and the outer wheel speed up?

TL;DR: The kinematic constraint imposes the redistribution of forces on the four wheels. This redistribution is permitted due to the car differential. IMHO it is easier understand this if you first ...
NMech's user avatar
  • 24.3k
8 votes

How many power strokes per rotation in a 3 cylinder engine?

Each cylinder produces a power stroke for every (2-stroke engine) or every other (4-stroke engine) rotation of the crankshaft. A 3-cylinder, 4-stroke engine will produce 3 power strokes for every 2 ...
Dave Tweed's user avatar
  • 6,874
8 votes

Why do cars have mirrors for rear view rather than cameras?

All the points mentioned by others are factors, but the true answer (i believe) is: Why cameras (and obviously displays) are not used instead of mirrors? The law (regulations on street ...
agent provocateur's user avatar
8 votes

Are front wheel drive vehicles inherently flawed?

Do the math. Wheel slippage isn't a issue unless you are trying to accelerate exceptionally hard. In practice, front wheel drive cars usually have better accelerating traction because the load on ...
Olin Lathrop's user avatar
  • 11.4k
8 votes

Why do electric cars claim "instant torque?"

ICEs (internal combustion engines) take some time to ramp up their output torque. Various mechanical systems have to react before more mixture is injected into cylinders, and that then makes more ...
Olin Lathrop's user avatar
  • 11.4k
8 votes

Is it possible to build an efficient Electric Vehicle engine with minimal to no computing control systems?

Yes, it's possible, but electronics do it cheaper, lighter, and in a more sophisticated manner than what electro-mechanicals can do it. You can also tweak software to tune a basic design. With electro-...
Phil Sweet's user avatar
  • 4,707
8 votes

On a car with all-wheel drive, how does the engine provide the angled front wheels with power?

You could also include front-wheel drive in your question. It would be enlightening for you to look at what radio control rock crawlers do. It has much of the excess of a full-sized car stripped away. ...
DKNguyen's user avatar
  • 5,546
8 votes

Why are bulldozers so slow?

Because the tracks or tyres and suspension needed for sufficient ground contact when pushing, dozing or grading does not match the suspension etc needed for higher speed situations. Even the ...
Solar Mike's user avatar
  • 15.6k
8 votes

Why are bulldozers so slow?

They need to be heavy for traction, which makes them too heavy for speed. To have enough friction between ground and tracks, the machine needs to be very heavy. The Caterpillar D9 you mention weighs ...
jpa's user avatar
  • 1,943
7 votes

Why do cars have mirrors for rear view rather than cameras?

Replacing all car mirrors with cameras is not a good idea. All it does is add unnecessary cost to a vehicle, and the cameras would actually not be quite as good as a standard mirror. The existing ...
Jason Hutchinson's user avatar
7 votes
Accepted

Why can't energy be entirely recovered from a moving car's rotating wheels?

Get a small DC motor from a cheap toy or something and put a gear or a flywheel or something on the shaft to make it easy to spin with your fingers. You should find these in the toy as well. Ask your ...
ChP's user avatar
  • 638

Only top scored, non community-wiki answers of a minimum length are eligible