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The instantaneous velocity at a point in time is equal to the average velocity over any time interval that the point is in the middle of.   So if you want the instantaneous velocity at 5 seconds, find the slope of the line between points on the curve at 4 and 6 seconds, or 3 and 7 seconds, etc.

Note: Someone apparently downvoted the above answer without understanding, so I'll explain.   The secant line to a continuous curve is defined as the line connecting any two points on the curve.   In the interval between those two points for an increasing function, the slope of the tangent to any point changes from a value less than that of the secant line to a value greater than that of the secant line.  So there must be a point where the slope of the tangent is the same as that of the secant line (in other words, they are parallel).   This is the idea that leads to the derivative of a function in calculus.   For a parabolic position vs. time curve, that point is located in the middle of the time interval.

The instantaneous velocity at a point in time is equal to the average velocity over any time interval that the point is in the middle of.   So if you want the instantaneous velocity at 5 seconds, find the slope of the line between points on the curve at 4 and 6 seconds, or 3 and 7 seconds, etc.

Note: Someone apparently downvoted the above answer without understanding, so I must have been too brief or unclear.  I'll explain.   The secant line to a continuous curve is defined as the line connecting any two points on the curve.   In the interval between those two points for an increasing function, it can be seen that the slope of the tangent to any point changes from a value less than that of the secant line to a value greater than that of the secant line.  So there must be a point where the slope of the tangent is the same as that of the secant line (in other words, they are parallel).   This is the idea that leads to the derivative of a function in calculus.   For a parabolic position vs. time curve, that point is located in the middle of the time interval.  The slope of the tangent at that point, and the slope of the secant line that it's in the middle of, are equal to the instantaneous velocity.

The instantaneous velocity at a point in time is equal to the average velocity over any time interval that the point is in the middle of. So if you want the instantaneous velocity at 5 seconds, find the slope of the line between points on the curve at 4 and 6 seconds, or 3 and 7 seconds, etc.

Note: Someone apparently downvoted the above answer without understanding, so I'll explain. The secant line to a continuous curve is defined as the line connecting any two points on the curve. In the interval between those two points for an increasing function, the slope of the tangent to any point changes from a value less than that of the secant line to a value greater than that of the secant line. So there must be a point where the slope of the tangent is the same as that of the secant line (in other words, they are parallel). For a parabolic position vs. time curve, that point is located in the middle of the time interval.

The instantaneous velocity at a point in time is equal to the average velocity over any time interval that the point is in the middle of.   So if you want the instantaneous velocity at 5 seconds, find the slope of the line between points on the curve at 4 and 6 seconds, or 3 and 7 seconds, etc.

Note: Someone apparently downvoted the above answer without understanding, so I'll explain.   The secant line to a continuous curve is defined as the line connecting any two points on the curve.   In the interval between those two points for an increasing function, the slope of the tangent to any point changes from a value less than that of the secant line to a value greater than that of the secant line.  So there must be a point where the slope of the tangent is the same as that of the secant line (in other words, they are parallel).   This is the idea that leads to the derivative of a function in calculus.   For a parabolic position vs. time curve, that point is located in the middle of the time interval.

The instantaneous velocity at a point in time is equal to the average velocity over any time interval that the point is in the middle of. So if you want the instantaneous velocity at 5 seconds, find the slope of the line between points on the curve at 4 and 6 seconds, or 3 and 7 seconds, etc.

The instantaneous velocity at a point in time is equal to the average velocity over any time interval that the point is in the middle of. So if you want the instantaneous velocity at 5 seconds, find the slope of the line between points on the curve at 4 and 6 seconds, or 3 and 7 seconds, etc.

Note: Someone apparently downvoted the above answer without understanding, so I'll explain. The secant line to a continuous curve is defined as the line connecting any two points on the curve. In the interval between those two points for an increasing function, the slope of the tangent to any point changes from a value less than that of the secant line to a value greater than that of the secant line. So there must be a point where the slope of the tangent is the same as that of the secant line (in other words, they are parallel). For a parabolic position vs. time curve, that point is located in the middle of the time interval.