you need
• - handle;
• - paper records.
Guide
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The simplest case - the movement of one body at a predetermined uniform speed th.We know the distance that the body passed.Find time the way: t = S / v, h, where S - the distance, v - average speed body.
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second example - to counter the movement of bodies.From point A to point B moves the car from speed th to 50 km / h.Meet him from B simultaneously rode a moped with speed th 30 km / h.The distance between points A and B, 100 km.It takes time to find , through which they will meet.
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Designate a meeting point of the letter K. Let the distance AK, who drove the ca
r, will be x km.Then the path rider is 100 km away.From the condition of the problem that time in the way of the car and moped same.Make the equation: x / v = (Sx) / v ', where v, v' - the speed of the car and a moped.Substituting the data, decide the equation: x = 62,5 km.Now find time : t = 62,5 / 50 = 1.25 hours, or 1 hour 15 minutes.
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third example - are given the same conditions, but the car drove about 20 minutes later a moped.Determine how long the road will be a car to meet with a moped.
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Make an equation similar to the previous one.But in this case the time moped path will be 20 minutes longer than that of the vehicle.For the equalizing part, subtract one-third of an hour from the right side of the expression: x / v = (Sx) / v'-third.Find X - 56.25.Calculate time : t = 56,25 / 50 = 1,125 hours or 1 hour 7 minutes 30seconds.
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fourth example - the problem on the motion of bodies in the same direction.Car and moped with the same speed move from point A. We know that the car left half an hour later.After some time he will catch a moped?
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In this case, the distance will be the same that drove vehicles.Let time in the way the car is x hours, then time moped on the road will be x + 0,5 hours.You obtain the equations: vx = v '(x + 0,5).Solve the equation by substituting the speed and find x - 0,75 an hour or 45 minutes.
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fifth example - a car and a moped with the same speed move in one direction, but a moped drove from point B, at a distance of 10 km from the point A, half an hour earlier.Calculate, after some time after starting the car overtake a moped.
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distance that drove the car for 10 km more.Add the difference to the path of the motorcyclist and equalize expression: vx = v '(x + 0,5) -10.Substituting the values ​​of speed and decided to it, you will get the answer: t = 1,25 an hour or 1 hour 15 minutes.