IPC
HS/Science
Unit: 07 Lesson: 01
Describing and Calculating Motion KEY
Objectives:




Distinguish between distance and displacement.
Calculate average speed.
Explain the difference between speed and velocity.
Interpret motion graphs.
1. Define Motion: a change in position based on a frame of reference
2. Speed describes the distance an object travels over time.
3. Speed considers two factors:
a. distance
b. time
4. Define Instantaneous Speed: the speed at a single instant in time (speedometer
reading in a car)
5. Define Constant Speed: a speed that is not changing over time
6. Define Displacement: the distance and direction of an object’s final position from its initial
position
7. Define Distance: the total path traveled
8. Define Vector: a quantity that has a specific size and direction (displacement, velocity,
acceleration)
Remember: Slope of the line is speed.
Speed Equation:
speed = v = distance
time
v = displacement
time
SI Unit: meters per second, m/s
©2012, TESCC
11/04/12
Page 1 of 3
IPC
HS/Science
Unit: 07 Lesson: 01
9. The graph below shows the motion of a cheetah over a five second period of time. Use the graph
to answer the questions.
a. How many meters did the cheetah travel after one second? 30 m
b. How many meters did the cheetah travel after three seconds? 90 m
150
Distance (m)
120
90
60
30
0
1
2
3
2
0
Time (sec)
4
5
Describe a Distance-Time Graph:
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



Distance is plotted on the vertical (y) axis.
Time is plotted on the horizontal (x) axis.
Have an appropriate scale that covers the range on each axis.
Plot data and draw a line to connect the points.
The slope of the line is the object’s speed.
10. Define Average Speed: This is the total distance covered divided by the total travel time.
v = d/t
©2012, TESCC
11/04/12
Page 2 of 3
IPC
HS/Science
Unit: 07 Lesson: 01
11. The graph below shows the motion of a cyclist over a six hour period of time. Use the graph to
answer the following questions.
a. What is the cyclist’s speed during the first two hours? 20 km/2 hrs = 10 km/hr
b. What is the cyclist’s speed between two and three hours? 20 km/1 hr = 20 km/hr
c. What is the cyclist’s speed between three and four hours? 0 km/hr
d. What is the cyclist’s speed between four and six hours? 20 km/2 hrs = 20 km/hr
e. Was the cyclist’s speed constant over the entire ride? No
f. What was the cyclist’s average speed over the entire ride? 60 km/6 hrs = 10 km/hr
Distance (km)
80
60
40
20
0
1
2
3
4
5
6
7
Time (hr)
©2012, TESCC
11/04/12
Page 3 of 3