Name: _________________________ Physics 11 Blk: _________

Lesson 4 Describing Motion with Position vs. Time Graphs

A person walking along a straight line is being timed while their position from the starting point is

recorded. The data is recorded in the following table:

Time (s) 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00

Distance

(m)

4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0

Graph the data below:

a) What is the y intercept of this graph?

b) What is the slope of this graph?

c) What is the equation of this graph?

Key Idea: The slope of a displacement vs time graph is the velocity, What if we have a changing

velocity? Ex. 2) Describe what is happening over each interval of the distance vs time graph below:

a) Find the average speed over each interval:

Name: _________________________ Physics 11 Blk: _________

b) What is the average velocity for the entire trip?

c) What is the average speed for the entire trip?

Average Slope vs Instantaneous Slope

Constant Velocity

Positive Velocity

Positive Velocity

Changing Velocity (acceleration)

Slow, Rightward(+) Constant Velocity

Fast, Rightward(+) Constant Velocity

Name: _________________________ Physics 11 Blk: _________

So, we can use this approach to approximate the slope of a curve in order to find the instantaneous

velocity.

Graph of distance Vs time

Name: _________________________ Physics 11 Blk: _________

a) Find the instantaneous velocity for every 30 minute interval on the graph above. Clearly show

the line that you used to calculate the instantaneous slope on the graph, and show your

calculations for the slope as well.

b) At what time(s) has this person come to a stop?

Negative (-) Velocity

Slow to Fast

Leftward (-) Velocity

Fast to Slow

Check Your Understanding

1- Use the principle of slope to describe the motion of the objects depicted by the two plots

below

1. Determine the velocity (i.e., slope) of the object as portrayed by the graph below.

Name: _________________________ Physics 11 Blk: _________

1- What is velocity of the object moving in this graph at 4 seconds?

2- What is the velocity of the object moving in this graph at 6 seconds?

3- What is the velocity of the object moving in this graph at 10 seconds?

4- How far did this object in this graph go in 5 seconds?

5- What is the average SPEED of this object after 15 seconds?

6- What is the total displacement after 15 seconds?

7- What is the average VELOCITY of this entire graph's motion. Answer in a fraction