# Instantaneous velocity in a graph

• doc2142
In summary, the student is struggling to plot the instantaneous velocity of a glider as a function of time for a linear kinematics lab. They have provided data points for position and time intervals, but are unsure how to accurately graph the instantaneous velocity. They have attempted to trace the points and use the average velocity, but have been unsuccessful in getting a straight line graph. The student is seeking help to understand how to accurately plot the data.
doc2142

## Homework Statement

http://homework.sdmesa.edu/cmona/195/MP195AFiles/1%20linear%20kinematics%20lab.pdf
That is the link to my lab.
My question is on page 5:
Plot instantaneous velocity as a function of time.
Recall that your data only indicates the average velocity of the glider for each time interval and that
for constant acceleration, the instantaneous velocity of the glider at the middle of each time interval is
equal to the average velocity of the glider during that time interval
Plot the instantaneous velocities of the glider as a function of time. Remember that your first velocity
occurs at 0.05s, and the next is at 0.15s, 0.25s, …etc.

My data:
X(CM)-T(S)
0-0
4.9 - .1
10.8 - .2
17.5 - .3
25.2 - .4
33.8 - .5
43.3 - .6
54.1 - .7
65.1 - .8
77.3 - .9
90.2 -1.0
104.2 - 1.1
119.2 - 1.2
134.9 - 1.3
151.7 - 1.4

## Homework Equations

I have no idea how to graph the instantaneous velocity, I tried and tried, but for some reason the graph i get is a curve, a very steep curve, i was told it should be more of a line. This curve also screws up later calculation in the same lab.

## The Attempt at a Solution

I tried following the instruction, from what I understand, using my first graph points. I take the .15s and trace it and see what velocity I get and use that as my instantaneous velocity... I know that is wrong because every time I try that my numbers are way off!

Last edited by a moderator:
I was told it should look like a line graph, but when I try that, I end up with a curve. Please please help!

## What is instantaneous velocity?

Instantaneous velocity is the rate of change of an object's position at a specific instant in time. It is the slope of the tangent line to the position-time graph at that instant.

## How is instantaneous velocity different from average velocity?

Instantaneous velocity is the velocity at a specific point in time, while average velocity is the overall velocity over a certain period of time. Average velocity is calculated by dividing the total displacement by the total time, while instantaneous velocity is calculated by taking the limit as the change in time approaches zero.

## How can you determine instantaneous velocity from a graph?

To determine instantaneous velocity from a graph, you can find the slope of the tangent line to the curve at a specific point. The steeper the slope, the greater the instantaneous velocity at that point.

## What does a horizontal line on a position-time graph indicate about instantaneous velocity?

A horizontal line on a position-time graph indicates that the object is not moving, therefore the instantaneous velocity at that point is zero. This is because the slope of a horizontal line is zero.

## Can instantaneous velocity ever be negative?

Yes, instantaneous velocity can be negative. This means that the object is moving in the negative direction, or in the opposite direction of the positive direction on the graph. This can occur when the slope of the tangent line is negative, indicating a decrease in position over time.

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