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# Instantaneous speed and velocity

Instantaneous speed is a measurement of how fast an object is moving at that particular moment. Instantaneous velocity is a vector quantity that includes both the speed and the direction in which the object is moving. Learn how to find an object’s instantaneous speed or velocity in three ways - by using calculus, by looking at the slope of a given point on a graph of an object’s rate vs. time, or by using kinematic formulas if the object’s acceleration is constant. Created by David SantoPietro.

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• what is the formula to find instantaneous velocity using calculus?
• Using calculus, you would find the derivative of the function for the objects position to find the velocity at any given point.
• How would you know at which angle to draw the tangent line on a graph to find the instantaneous velocity. By angle I mean how do you know how to draw that line if you only have one point? Thanks.
• The point forces the angle. If you draw the tangent line any more or less steep it would no longer to a tangent. It would be a secant line.
• I'm not sure I understand how to find instantaneous velocity and speed. I did not learn calculus yet and I don't know how to find the slope of a curve at a point in the curve. Of course when the average and instantaneous velocity are the same it's easy, but is there a way to figure it out that works for all scenarios?
• I think if you did not learn calculus yet, then you will not be expected to calculate the instantaneous speed; more likely the speed over a given time. But it is a very interesting question... (and nicely presented)

I will chew it over further...
• wahat do you mean by Vi?
• initial velocity. if u find it confusing to use it, like in formulas such as Vf = Vi + at where it says final velocity is equal to initial velocity plus the product of acceleration and time, you simply use:-
v = u + at --> where 'v' is the final velocity, 'u' is initial velocity, 'a' is acceleration and 't' is time
• Good video but it was so fast. Kinda wish Sal taught it
• can you talk about the scalars i don't know much about it since you didn't really say how to figure out how to get the way the person went or how far you didn't talk about that just the vectors so in the next video can you please talk about scalars?
• A scalar quantity is just the magnitude without a direction as far as i understand. When you give something a direction (like which way a force is acting or which way a car is going) then its a vector. Like on a car, you have a speedometer, not a velocimeter, because the car just tells you how fast you are going, not which direction.
• at in video
i didnt understand why it's 0/0 ?
• Is there an easy way to find the average speed of an object without using calculus? I haven't learned calculus yet.