Answer
When you say 'run him' I hope this is a racehorse, since a pleasure or show horse has no need to run. Don't pull on the reins and expect a running horse to pay attention to that. If you need to stop in an emergency, pull on one rein with both hands to turn into a tight circle and keep circling until the horse stops. A horse will not trip if you do this. A horse does not really care if you fall off, and many new to riding would prefer this if you do fall off.
Another Answer
For what it's worth, a horse "running" isn't restricted to racing. A gallop out on the trails is great, and many gaming horses obviously have to run. Pleasure or show horses aren't restricted to walk/trot (or whatever intermediate gait it may have)/canter - galloping is fine. Now, with that being cleared up, it's not advised that you do a one-rein stop on an untrained or unbalanced horse - contrary to what the other person said, a horse CAN and WILL fall if turned too fast, too soon. A one rein stop needs to be taught, not just thrown on a horse. Learning how to disengage the hindquarters is far more important that turning in a bunch of circles. Starting from the ground, teach the horse to shift his hindquarters away from your hand - not just stepping around, but actually crossing his hind legs to move away from you. To do this, he needs to be light in the halter (aka gives easily side to side) and will move off of pressure. It may take awhile to get, but be patient and persistent, and it'll happen. Once he's got it on the ground, both sides, transfer into the saddle. Take up on one rein and apply the same side leg slightly behind the girth (you may have to exaggerate while teaching it) until you feel the horse take a big step over with his hindquarters. Eventually, if done correctly, taking away his hindquarters (or, essentially, his motor) will stop a horse from bolting. With a horse that is already bolting, circling is fine, but don't yank him immediately into a tiny circle - that will throw him off balance if he doesn't know how to carry himself properly and can be dangerous to you and the horse.
As for stopping a horse who is not out of control, you need to start small. First, a good stop comes from a light mouth and a horse sensitive to your seat. Start with a walk, and do walk-stop transitions. Sink your weight into the saddle and do not pull, but set your hands on the pommel of your saddle. When the horse stops and drops his nose, immediately release (but don't walk forward!) and praise. Do this at a walk until he is responding from just the shift of your weight. Then do some walk-trot-walk transitions. then trot-stop. So on, and so forth. It takes work, time, and patience, but it is worth it in the end to get a light, immediate stop.
ANOTHER ANSWER
***In an emergency every rider should know how to do a one-rein stop. If the horse gets out of control and you can't stop it, slide your left hand quickly up the left side of the rein to the horse's mane, take a firm grip on the mane with the rein in your left hand. Then pull the horses head to the right with the other rein to turn it in a circle, this will slow the horse down so you can stop it. Keeping the left hand on the horses mane enables you to keep your balance and stay with the horse as it turns. Be prepared for the horse to turn sharply.
Another Answer?
` We used to have a horse who used to be a beast at forward, and stopping not so much... no matter what gait it would take him 3-5 times around the round pen of hard pulling for him to stop. The circle trick above is what we used to teach him, and it really works! Don't push him too hard and throw in tight circles right away. Work with circles first, on the ground. Make sure there is good footing where you are at too! Accidents are bad, and could create a bad experience with the whole "stopping thing", making your horse wants to stop less and become nervous. Bigger problems there. But circles are a good idea. If you're pulling super hard on the bit, try changing bits. Having a more serious bit that the horse is more sensitive to is better then hurting the horses sensitive mouth tissues. When they are good at stopping, switch bits to a softer one, and work on stopping there when they have the idea and they are better at it! :) ` Hope this helps at all with the whole other paragraphs above o.O hehe.
it takes a while for the horse to open its moulth again
It depends greatly on the repair needed and the tools you have on hand in determining how long it takes to repair brakes and brake services. If you don't have that have a professional do it.
as long as it takes - approximetly 3 to 9 hours
Yes, just like humans do. Some horses are bred to race long distances, and because of that it takes them longer to get tired of running.
i was told it takes about 6 years but not completely positive
For a young horses' joints to fully fuse, it takes 3-5 years. This is why horse racing is very dangerous because the horses are not fully developed. Do not jump/race/work hard with immature horses!
As long as it takes. You didn't specify a model (remember, Kenworth makes Class 5 through Class 8 trucks), you didn't specify a brake system (S-cam air brakes, hydraulic brakes, hydraulic disc brakes, air disc brakes, air wedge brakes, or air piston brakes), and we don't know your level of technical experience.
The answer to how long it takes for a butterfly to transform is usually 2-6 weeks, and to improve your question.... How long does it take for a caterpillar to transform into a butterfly?
It does not decompose, but brakes up into tiny pieces and eventually turns into plastic dust. This process takes hundreds of years.
I don't undertsand what you mean. Is it how long are horses? That varies.
If you get the low priced brakes they will end up costing you much more in the long run. If you get the more expensive brakes you will save more in the long run.
"Depending on who does it and how many brakes are being worked on, it can range between 45 minutes and an hour (for the average person working on just the front brakes) or 3 to 5 hours for all brakes. You may also consider the time it takes to retrieve the parts (or for the person who is doing the service for you)."