Download Balanced Forces Worksheet 1

Name
Period
Date
1. A cardboard box sits at rest on a rough, concrete,
horizontal floor.
a. Draw a qualitative (no numbers) velocity vs. time graph
for the box showing the time period while it sits at rest.
velocity
Balanced Forces Worksheet 1
time
c. Since the shape of the box is unimportant,
shrink it to a point. Then draw and clearly
label each force acting on the box. Be sure
to note the relative sizes of the various
forces. (i.e. FN  Fg , or FT  F fk etc.)
d. Circle the correct answers.
Is the box moving at constant velocity? Yes
Are the forces balanced?
Yes
No
No
2. A person now shoves the box horizontally so that it begins
to move.
a. Draw a qualitative (no numbers) velocity vs. time graph
for the box showing the time period while the person is
touching the box and shoving it.
velocity
b. Draw a system schema for this
situation.
time
b. Draw a system schema for the
time period while the person is
shoving the box.
c. Draw and label a force diagram for the box
during the time period while the person is
shoving the box. Be sure to note the
relative sizes of the various forces.
d. Circle the correct answers.
Is the box moving at constant velocity? Yes
Are the forces balanced?
Yes
No
No
page 2
3. The box now loses contact with the person’s hands and
slides across the rough floor.
a. Draw a qualitative (no numbers) velocity vs. time graph
for the box showing the time period after the box loses
contact with the person’s hands.
velocity
Balanced Forces Worksheet 1
time
b. Draw a system schema for the
box after it leaves contact with
the person’s hands.
c. Draw and label a force diagram for the box
after it leaves contact with the person’s
hands. Be sure to note the relative sizes of
the various forces.
d. Circle the correct answers.
Is the box moving at constant velocity? Yes
Are the forces balanced?
Yes
No
No
velocity
4. Suppose that we could somehow succeed in making the floor completely frictionless.
Just as in problems #1-3 the box sits at rest for a while, then is pushed so that it
starts to move, and then loses contact
with the person’s hands and moves
across the now frictionless floor.
a. Draw a qualitative (no numbers)
velocity vs. time graph for the box
showing all three periods of time on
one graph.
time
b. Draw a system schema and a properly labeled force diagram for the time period
while the box is at rest on the horizontal floor. Be sure to note the relative
sizes of the various forces.
Circle the correct answers.
Is the box moving at constant velocity? Yes
Are the forces balanced?
Yes
No
No
Balanced Forces Worksheet 1
page 3
c. Draw a system schema and a properly labeled force diagram for the time period
while the person is still shoving the box.
Circle the correct answers.
Is the box moving at constant velocity? Yes
Are the forces balanced?
Yes
No
No
d. Draw a system schema and a properly labeled force diagram for the time period
after the box loses contact with the person's hands.
Circle the correct answers.
Is the box moving at constant velocity? Yes
Are the forces balanced?
Yes
No
No
velocity
5. Return to the case of the cardboard box resting on the concrete floor with some
friction. The box sits at rest for a while after which a person pushes it hard enough
to start it into motion, and then the person continues pushing so that it maintains a
constant velocity.
a. Draw a qualitative (no numbers) velocity vs. time graph for the box showing all
three periods of time on one graph.
time
Balanced Forces Worksheet 1
page 4
b. Draw a system schema and a properly labeled force diagram for the time period
while the box is at rest on the horizontal floor.
Circle the correct answers.
Is the box moving at constant velocity? Yes
Are the forces balanced?
Yes
No
No
c. Draw a system schema and a properly labeled force diagram for the time period
while the person is pushing the box so that it is speeding up.
Circle the correct answers.
Is the box moving at constant velocity? Yes
Are the forces balanced?
Yes
No
No
d. Draw a system schema and a properly labeled force diagram for the time period
while the box moves with a constant velocity.
Circle the correct answers.
Is the box moving at constant velocity? Yes
Are the forces balanced?
Yes
No
No
velocity
e. After pushing the box with a constant velocity for a while, you reduce your force
to half the value needed to maintain a constant velocity. Draw a new
qualitative (no numbers) velocity vs. time graph for the box showing all four
periods of time on one graph.
time