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Since now we have the basic concepts of kinematics, let's try now to apply them.

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In this video we are dealing with some very simple problems just to practice.

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For this is the kind of problems I will ask you to solve in the exam.

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We can start with changing the units of velocities.

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For example, from kilometers per hour into meters per second.

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We multiply 1000 times and we divide 3600, because one hour has 3600 seconds.

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So 36 kilometers per hour is the same as 10 meters per second.

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Conversely, to pass from meters per second to kilometers per hour, we just multiply 3600

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and divide by 1000, so in fact we multiply by 3.6, thus 20 meters per second is the same

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as 72 kilometers per hour.

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should practice this for the exam. Another typical exercise about velocity

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is finding the point where two mobiles meet. To do this, we are just dealing with

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mean velocities. In this case, two trains, one leaving Madrid, the other one

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Zaragoza, both at the same time, the one from Madrid at a speed of 200 km per hour

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and the one from Zaragoza at 150 km per hour, must meet at a certain point

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and that point is just the purpose of this exercise, finding it.

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Let's just remember that speed is the relationship between space and time.

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On the other hand, we know that when the two trains meet, the time will be the same for both.

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So we can derive the formula for time and then make both times the same number.

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And so we have obtained the key equation where S1 is the space between Madrid and the meeting point,

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s2, the distance from Zaragoza up to the meeting point, and v1, v2, their respective velocities.

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We can solve this, provided we know the total distance between Madrid and Zaragoza.

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In order to do this, we remove one variable using the given value of the total distance.

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Thus, we can write.

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this equation we have only one variable that we can derive just by multiplying

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in cross. Please try to follow this by writing on a paper by yourself. Now we

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can group the terms having S1 on the left side of the equation and so we can

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derive the value for S1. This means that the trains meet at 200 kilometers away from Madrid.

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Of course we can also calculate at what time and since the velocity for train 1 is 200 kilometers

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per hour, it's clear that it has spent just one hour. Well, that's all for the moment.

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Try to practice, write me your hands on it up, and watch the Padlet where I'm uploading

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an exercise that I expect you to send me back before Wednesday.