Download Worksheet 4

Interactive Physics Worksheet #4 — “One-D Motion”
Overview
Time Card
In “One-D Motion” we get quantitative about forces and accelerations for
the first time. We will limit our attention to forces and motions in one
dimension only. You will apply a force of adjustable magnitude to a body
of adjustable mass. You will examine graphs of the position, velocity, and
acceleration as functions of time and compare them to the actual motion
produced by the applied force.
Name:
Date
Time In
Time Out
Please “punch in” and “punch out” of the computer lab using the time card
at right and write your answers to each question on the worksheet itself in
the space provided.
Getting Started
Locate and open the Interactive Physics module—“One-D Motion”—in
the Physics 121 folder. When the window opens you will see a scene like
that shown in Figure 1.
The body has amass that can be adjusted
from 1 to 5 kg with the slider control on the
left. It is acted on by a force that is
adjustable between –10 N (downward) and
+10 N (upward) using the slider on the
right. You can also turn the force on or off
and display a one-dimensional coordinate
axis using the control buttons above the
sliders
The position, velocity, and acceleration of
the body are graphed as functions of time on
the three graphs on the right side of the
screen.
Begin by adjusting the force and noticing
that the red force vector changes its
magnitude and direction according to the
value chosen on the slider. Also try turning
the force on and off and notice the effect on
the display of the force vector. Finally, turn
Fig 1:
The startup screen from “One-D Motion”
on the display of the axis which runs from 30 m at the bottom of the screen to +=30m at the top. Notice that the body starts at x = 0 at t = 0.
Set the force to +4.00 N and the mass of the body to 2.00 kg. Make sure the axes are displayed and the force is on. Run the
simulation and notice that the body leaves small circular dots in its track every 1 second on the clock or 50 frames on the
“Tape Player.” Let the body move off the top of the screen and then stop the simulation and answer these questions:
Q1: What are the positions of the circular dots that are left at successive one second intervals? Do you see a pattern?
1
Can you explain this pattern in terms of the equation x = 2 a t2?
Q2: What does the acceleration versus time graph tell you about the acceleration of the body during this interval?
Given the applied force and the mass does this make sense?
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Q3: What does the velocity versus time graph tell you? What does the fact that the slope of this graph is constant tell
you about the rate at which the velocity is changing? How is this related to the acceleration?
Q4: What does the position versus time graph tell you? What does the fact that its slope is constantly increasing mean?
Now drag the frame counter at the bottom of the window back to frame 100 and note the time which should be 2.0 s. Turn the
force off and click on the “Run” button to restart the simulation from this point. Stop it when you get past frame 200.
Q5: Describe the motion and explain how it is related to the shapes of the three graphs during the interval from t = 2.0
s to t = 4.0 s.
Now drag the frame counter back to frame 200, set the force to –2.00 N, turn the force back on, and click on the “Run” button
to restart the simulation from this point. Let the simulation run past the point at which the forward motion of the body is
eliminated. Then stop the simulation and drag the frame counter back to that point.
Q6: How long does it take this force to bring the body to rest? How does this compare with the amount of time it took
the original force to bring the body “up to speed” in the first place? Why the difference?
Q7: What is the position of the body at the “turn around point”?
Q8: Assuming the force is maintained, at what time will the body get back to x = 0?
Try pushing the body around with varying forces and try to relate the graphs of x, v, and a versus time to the applied force and
to each other. Doing so should help you understand the relationships between these quantitites.
Well, we could spend a lot more time on this one, but we'll move on now to the final worksheet...
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