3:39 Another way to show this , since the angle is -45° for the downward ski slope, we have tan(-45) = y/x , or -1 = y/x . Therefore x = -y, and thus 20t = - (-4.9t^2) , and we have positive time.
@@MichelvanBiezen i had a question similar but the angle was 30 degrees i tried it by equating x=y tan 30 and then substituted the x and y with x=v/t and y=1/2 at^2 i made time subject to calculate time also i was given only horizontal velocity at the beginning as well which is 24.25 m/s, i got time to be around 8 sec and i followed with the Pythagoras theorem since i could find x and y with help of t and found the length of the ski diver traveled along the slope which was around 400m, not sure if this is also possible or even correct. ( the question wanted me to find the length of a slope and a ski diver was jumping and landing on a point on the slope and the initial velocity was horizontal only 24.25 m/s and an angle was given 30 degrees i had to find out the length of the sloped thee ski diver traveled from the initial to how far it landed )
Narek, Thanks for the comment. Yes, I am having fun posting all these videos. It is a lot of work, but it is great that so many people around the world seem to appreciate them. Enjoy.
When using the equations of kinematics (in projectile motion), direction is important. Since the acceleration due to gravity (g) is directed downward the value must be negative.
The word "supposed" may be a bit strong. It is true that dividing t^2/t may eliminate a solution. In this case it eliminates the t = 0 solution which is a mathematical possibility, but not a real life solution in this problem.
Can I use this method if my skier exits the jump at an angle (38 degrees up in my case) and lands on a slope downward (15 degrees below the horizontal) and use theta = 53 degrees?
Physics and equations go hand-in-hand. Equations are a method of representing physical phenomena in mathematical form. Sometimes you can also represent them graphically. We have a playlist that shows you how to use graphical methods as well. PHYSICS 2.5 - 1D MOTION : GRAPHIC SOLUTIONS Physics 2.5 - Motion In 1-D - Graphical Solution (1 of 12) Ex.1 Road Trip ua-cam.com/video/4TVlE9Lbojk/v-deo.html
@@MichelvanBiezen Up to first grade of college, I didn't use any of them, I was used to graph that is it. Yeah, equations are also derived from graphs, but anyway it is hard to memorize them, even thought that is the easiest way to solve a problem. But I realized I shouldn't just use graphs, because sometimes that is like inventing the wheel again :D
Picking the y = 0 point is arbitrary. Thus it doesn't matter if you call the the initial point the zero height of the final point, you get the exact same result. In this case it made it easier to determine the equations by placing the origin at the starting point.
Sir I have one doubt in this....I solved it by assuming the downward inclined plane to be the X axis.....n though I should have got the same ans....I didn't get the ans u got.....instead I got x=40.81m I wish to send u my ans so that u can tell me where I went wrong....is there any way to do so? plz help
Could you possibly explain how to set the coordinate plane? I'm very confused since you used Yf = h, and Yi = 0, yet had gravity set negatively? Shouldn't gravity be set positive, if we are increasing our distance towards the ground (Assumed that coordinate plane is positive in the downwards direction)
Then the problem would be a projectile problem with zero initial velocity in the y-direction. (there are many examples of such a situation on this channel).
Vy initial is the initial velocity in the y direction, which is indeed equal to zero. There is no vertical velocity component when the skier first reaches the slope.
instead of x=y (in the third column of the solution on the board) you can say that tan45=y/x.... or 1=y/x in this case; in the general case tan(theta)=y/x and cross multiply after evaluating the tangent ratio for theta :):):) BTW nice example Michel :)
What is the difference of this video from the other video #2/21 (ua-cam.com/video/yjjcHxvQ7gY/v-deo.html ) in terms of Ysub0? First video Ysub0 is not zero. Here, it is.
3:39 Another way to show this , since the angle is -45° for the downward ski slope, we have tan(-45) = y/x , or -1 = y/x . Therefore x = -y, and thus 20t = - (-4.9t^2) , and we have positive time.
Best way to do it and use any angle.
thats what i was looking for can u please explain this better cause my angle is 37 and the above method wont work
@@melodi9725 divide x by y and make it equal to tan(37), the angle inside the triangle.
man thank u😭❤️
Those videos are great, thank you,this is great practice,short and detailed enough
How would you do it if the angle was other than 45 degrees?
Exactly the same. You would need to calculate the slope for the equation y = mx + b
@@MichelvanBiezen i had a question similar but the angle was 30 degrees i tried it by equating x=y tan 30 and then substituted the x and y with x=v/t and y=1/2 at^2 i made time subject to calculate time also i was given only horizontal velocity at the beginning as well which is 24.25 m/s, i got time to be around 8 sec and i followed with the Pythagoras theorem since i could find x and y with help of t and found the length of the ski diver traveled along the slope which was around 400m, not sure if this is also possible or even correct.
( the question wanted me to find the length of a slope and a ski diver was jumping and landing on a point on the slope and the initial velocity was horizontal only 24.25 m/s and an angle was given 30 degrees i had to find out the length of the sloped thee ski diver traveled from the initial to how far it landed )
God bless you for these videos, sir.
Very, very informative and detailed.
Keep it up.
Narek,
Thanks for the comment. Yes, I am having fun posting all these videos. It is a lot of work, but it is great that so many people around the world seem to appreciate them.
Enjoy.
Sir,Have you done any videos on collissions ?
Sir what if we take inclined co-ordinate system and apply the formula for horizontal range. Will it affect our answer?
Hi. Why cant the Y0 (initially height) to be unknown while the Y(final height) to be zero?
That works as well. Try it and you'll see that you will get the same answer. (But it may be a bit more difficult to set up the equation)
Why we cannot use Range formula in this case, V initial squared multiplied sin2& and divided by g ?
To use the range equation, the object must start and end at the same height.
Great video sir! Helped me for my Physics GCSE Coursework
Thank you so much I was really struggling on a similar problem not realizing i could use y0=0 and y=h
Hi sir, why is g negative? I would think it is positive since the ski person is going downward.
When using the equations of kinematics (in projectile motion), direction is important. Since the acceleration due to gravity (g) is directed downward the value must be negative.
I thought you weren't supposed to divide by a variable ( 3:08) because it would eliminate a possible solution
The word "supposed" may be a bit strong. It is true that dividing t^2/t may eliminate a solution. In this case it eliminates the t = 0 solution which is a mathematical possibility, but not a real life solution in this problem.
Why not we use the range equation to solve for d?
The range equation only works if the starting point and the landing point are at the same elevation.
What would you do if the angle was not 45 degrees?
+Rachel Ellerd
Then you have to find the relationship between x and y using the linear equation y = mx + b.
"m" would be the tan of that angle, but what would "b" be?
How do we come to the conclusion that x=y? Maybe I just can't imagine such scenario (I'm not a skier :D)
When the slope is 45 degrees it can be represented by the linear equation y = x (from y = mx + b) where m, the slope, is equal to 1.
Can I use this method if my skier exits the jump at an angle (38 degrees up in my case) and lands on a slope downward (15 degrees below the horizontal) and use theta = 53 degrees?
Yes, just the slope equation will be different.
@@MichelvanBiezen thank you so much!
Sir why does x=y?
Since the angle of the slope is 45 degrees, the slope = 1, and therefore the ratio of y to x is 1:1
how would you find the max height
There is no "maximum height" in this problem.
@@MichelvanBiezen I think Cody is refering to the maximum height above the plane, d.
Why there is no vertical Vy downward initial velocity? in one of previous examples:"
" I have seen downward initial velocity component. "
" thank you
The motion of the skier is horizontal at the top.
I don't like using formulas in physics, why did you use that equation. Could you show that by drawing a graph of velocity etc.
Physics and equations go hand-in-hand. Equations are a method of representing physical phenomena in mathematical form. Sometimes you can also represent them graphically. We have a playlist that shows you how to use graphical methods as well. PHYSICS 2.5 - 1D MOTION : GRAPHIC SOLUTIONS Physics 2.5 - Motion In 1-D - Graphical Solution (1 of 12) Ex.1 Road Trip ua-cam.com/video/4TVlE9Lbojk/v-deo.html
@@MichelvanBiezen Up to first grade of college, I didn't use any of them, I was used to graph that is it. Yeah, equations are also derived from graphs, but anyway it is hard to memorize them, even thought that is the easiest way to solve a problem. But I realized I shouldn't just use graphs, because sometimes that is like inventing the wheel again :D
gravity affect the time ????
Yes it does
Y is Voy zero? Isnt is -20?
it depends on the reference point and the direction of positive.
why y initial is 0? in the pervious examples it was y final 0 thank you
Picking the y = 0 point is arbitrary. Thus it doesn't matter if you call the the initial point the zero height of the final point, you get the exact same result. In this case it made it easier to determine the equations by placing the origin at the starting point.
Sir I have one doubt in this....I solved it by assuming the downward inclined plane to be the X axis.....n though I should have got the same ans....I didn't get the ans u got.....instead I got x=40.81m
I wish to send u my ans so that u can tell me where I went wrong....is there any way to do so? plz help
Without seeing your work it would be difficult to figure out where you went wrong. My suggestion is to do the problem as I showed you in the video.
+Michel van Biezen
okay sir!!
show its parabolic and how its correlated with its derivative
That would require a new video.
Could you possibly explain how to set the coordinate plane? I'm very confused since you used Yf = h, and Yi = 0, yet had gravity set negatively? Shouldn't gravity be set positive, if we are increasing our distance towards the ground (Assumed that coordinate plane is positive in the downwards direction)
+Matt I As in all kinematics problems it is recommend to use the standard x-y coordinate system (up = positive and down = negative). g = - 9.8 m/sec^2
what will happen to horizontal Vx velocity if it is 90° . will it be 0 or equal to initial velocity? thank you
Not sure what you mean by the word "it"
if you are in a rush use this formula D=2V^2cos(theta)/gcos(theta)^2 just put all of that in an advance scientific calculator just on that problem
why do you do this :x=y?
Since the slope is 45 degrees the relationship between x and y is 1 to 1.(magnitude)
Paolo Andreozzi , since tan theta= perpendicular/base, and we know that tan 45 =1 so it follows x=y. Enjoy!
I mean the angle teta. if we change from 45 to 90
Then the problem would be a projectile problem with zero initial velocity in the y-direction. (there are many examples of such a situation on this channel).
thank you it was really helpful
why vy0 is 0?..there is an angle .so shouldn't we use it to find vy0?
Vy initial is the initial velocity in the y direction, which is indeed equal to zero. There is no vertical velocity component when the skier first reaches the slope.
thank you ver much ^^
what if X and Y components are not simillar
+Discover your tallent
Then you have to use the algebra equation y = mx + b to solve the relationship between x and y.
instead of x=y (in the third column of the solution on the board) you can say that tan45=y/x.... or 1=y/x in this case; in the general case tan(theta)=y/x and cross multiply after evaluating the tangent ratio for theta :):):) BTW nice example Michel :)
You earned a new subscriber my friend!
Plus, do you have videos specifically for Calc 2?
Yes we have hundreds of videos on calculus 2. If you go to the home page of the channel you'll see how they are organized.
i did not understand being y negative although it is a distance and must be positive
With the equations of kinematics, down and to the left is considered negative.
show calculation in textbook strong notation
The purpose of these videos is to explain what cannot be understood from textbooks.
why is x=y
Because the incline is a 45 degree slope (rise = run)
thank you..
Why you do x=y done sir thanks you
The slope is 45 degrees. Which is the y = mx + b (upside down) becoming x = y
What is the difference of this video from the other video #2/21 (ua-cam.com/video/yjjcHxvQ7gY/v-deo.html ) in terms of Ysub0? First video Ysub0 is not zero. Here, it is.
Awesome help
😊
Thank you very much sir
you are welcome.
rip to the skiier 😂
Needs to be careful indeed.
I got the same result but I did not have a problem with negative y because I wrote that y = 0 and then I got y0 = 4.91t**2 sry for bad english
Yikeees! 😮 That' s fast! .
..and far!
Quite a jump!
nice
Thanks
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What is your background level of mathematics? Understanding physics does require a certain level of understanding of mathematics.