Student __________________
Class ___________
Date ____________
Average Speed and Instantaneous Velocity – Answer Key
The positions of a moving car at various times are shown in the table and graph below.
Position
A
B
C
D
E
F
t (s)
0.0
10.
20.
30.
40.
50.
x(m)
30.
52
38
0.0
-37
-53
1. What is the average velocity of
the car during the first 10 seconds?
2. What is the instantaneous velocity
of the car at point A?
We find the slope of the green line which is the tangent with the curve at point A. To do this
we extend the line until it hits the grid so we can read the coordinates of the other point.
This answer is estimation, so there is some margin for error (not too much though!).
3. What is the instantaneous velocity of the car at point D?
We construct a green line at point D which is the tangent with the curve at point D. We have
to be careful not to intersect with the curve. If we do that the line is not a tangent anymore.
To calculate the slope of this tangent we extend the line until it hits the grid so we can read
the coordinates of the other point. Of course one of the points can be point D.
This answer is estimation, so there is some margin for error (not too much though!).
4. What is the average velocity of the car for the entire trip?
5. What is the instantaneous velocity of the car at point F? Zero, because the tangent is flat.