Is this possible to have a single pedal (for brake) for both wheels in motorcycle?

Yes it is. Look into Moto Guzzi, they have a system where you only use the brake pedal. The brakes are linked together in a very simple arrangement. Both front and rear are activated simultaneously when you apply pressure to the pedal. They also have a front brake for extra braking power, but is only supposed to be used when the pedal is not enough.

The reason the brakes are separate in other bikes is because you are supposed to squeeze the front to transfer the weight to the front wheel, increasing the size of the contact patch of the tyre against the road before squeezing harder with the added tyre grip and simultaneously applying more pressure to the rear brake before easing off as the bike slows. Where this fails is if the rider panics in an emergency and grabs the front brake lever, causing the front wheel to skid, leading to a loss of control. Or when the rider has only ever learned to use one or other of the brakes, which also leads to a skid in a situation where hard braking is required.

If you practice braking and become good at it then you have more control over the effects of the brakes than if you have a linked system.

The Moto Guzzi pedal system isn't very popular amongst riders who are not used to it, and although some owners love it, other owners have replaced the brakes for some standard ones.

The advent of motorcycle ABS systems means that the safety advantage of the Moto Guzzi system is now fairly obsolete.

The main reason the brakes in most bikes are not linked is because riders don't want it that way.

It is, but it's not a good idea to have all of the braking power in one pedal or lever on a motorcycle. Motorcycles are single track vehicles and if one of the tires starts skidding because you cannot modulate the brakes separately you may have an accident.

That being said, there are bikes that have linked brakes where the foot pedal activates the rear caliper and one of the pistons in the front caliper and the front brake lever activates at least one of the pistons in the rear caliper along with 4 pistons in the front brake. This gives you more braking power with either brake without overpowering both wheels.

Of course, if you have antilock brakes on your motorcycle, you can link the brakes with more confidence and some bike manufacturers have done just that.

Pedal Motorcycle

Several years ago manufacturers (including BMW and Honda) were producing bikes with linked brakes, applying the front brake would also partially apply the rear (and vice versa on some systems). However, the fact is that for most modern bikes by far the most effective braking is done with the front and the rear is rarely required.

It's possible, but when riding as opposed to driving, you apply a different balance of braking forces to the front & rear tyres depending on whether road is wet or dry. Better to have independent control capabilities.

simple LAW

the LAW requires that ANY motorvehicle designed intended adapted or made for the road MUST have two seperate methods of stopping the vehicle.

This is why you have a hand brake or " safety" brake on a car as well as PARK on auto trans and the footbrake

SO on a bike you have seperate braking systems SOME like the Aprilia MANA and the PIAGGIO Mp3 have seperate PARK brakes that hold the rear wheel independant of the rear wheel brake

So to answer your question

Law dictates it

Yes, on my Honda VTX when you apply the foot brake it applies 80% braking to the rear and 20% to the front. The hand lever only works the front.

fairly inspite of you've written is completely astounding for the indian roads. the most perfect became the marigold garland and the opposite equipment. large paintings you should submit this to a favored mag or newspaper.

On all vehicles, without exception, it is far better to use the back breaks first, or, for two wheal vehicles the rider might easily be pushed over the handlebars. For four, or more wheelers, it is due to the tires gripping the surface of the road better, this way, while breaking.