Tabletop Hovercraft
Lesson 1: Activity 2
Introduction to Force Diagrams
Qualitative
Name________________________
Date_______________Bell_______
A force is a Push or a pull. A force diagram is a useful tool to analyze the forces acting on an
object, and make predictions about its motion.
Prelab –
1. What do you think it means when we say the forces acting on an object are “balanced”?
Describe an example.
2. What affect do you think “balanced” forces will have on the motion of an object?
3. Describe an example of an object with “unbalanced” forces acting on it.
4. What affect do you think this will have on the motion of an object?
Force Diagrams allow us to represent simply the important aspects of the forces acting on an
object so it can be analyzed.
1. Use a circle to represent the object.
2. Use arrows to represent each force. All arrows should start touching the circle, and
pointing away in the direction the force is acting
3. The length of the arrow represents the strength of the force.
Complete the chart for the object underlined in the description for each situation below.
Consider using the following to label your forces:
Gravity, Tension, Friction, Air Resistance, Normal force, push, pull, buoyancy
Description
Ex.1) A cat sits
motionless on a rug.
Ex. 2) A softball player
slides into home base.
Force diagram
(label all forces)
Are forces
balanced or
unbalanced?
(∑F=0 or ∑F≠0)
Will the motion be
constant or
change? How will
it change?
Description
1. An Ice skater moves
across frictionless ice
with a constant speed.
2. A chandelier is
suspended from the
ceiling by a chain.
3. A book is being
pushed across a table top
with a constant speed.
3. A Bucket of water is
being raised from the well
at a constant speed.
Force diagram
(label all forces)
Are forces
balanced or
unbalanced?
(∑F=0 or ∑F≠0)
Will the motion be
constant or
change? How will
it change?
Description
4. A Skydiver who has
just left the plane is
speeding up as he falls.
5. A skydiver is falling at
a constant velocity after
he has deployed his
parachute
6. A ball was thrown into
the air and is rising to the
top of its trajectory (path).
7. A ball is at the top of a
parabolic trajectory, just
before it begins to fall
back down.
Force diagram
(label all forces)
Are forces
balanced or
unbalanced?
(∑F=0 or ∑F≠0)
Will the motion be
constant or
change? How will
it change?
Description
8. A cork is floating in a
bowl of water.
8. An airplane is flying
straight and level through
the air.
9. A nail has been picked
up by a magnet.
10. A hovercraft glides
across a flat table
Force diagram
(label all forces)
Are forces
balanced or
unbalanced?
(∑F=0 or ∑F≠0)
Will the motion be
constant or
change? How will
it change?
Tabletop Hovercraft
Lesson 1: Activity 2
Introduction to Force Diagrams
Quantitative
Name________________________
Date_______________Bell_______
Find the values of the forces identified below. Be sure to pay attention to the net
force as well.
1. Fnet=0 N
2. Fnet =0 N
5N
3. Fnet= 10 N upward
50 N
___
___
10 N
___
___
60 N
5. Fnet= 30 N upward
4. Fnet= 50 N right
____
70 N
___
60 N
___
20 N
10 N
70 N
6. Fnet = _________
7. Fnet= _________
50 N
55 N
25 N
30 N
100 N
55 N
8. Fnet= 15 N left and 10 N down
9. Fnet = 0 N
115 N
115 N
_____
____
10. Fnet= 0 N
____
11. Fnet= 15 N down
65 N
75 N
25 N
105 N
13. Draw a force diagram that has a
Net force of 50 N down
12. Fnet = 20 N right
10 N
____
72 N
____
30 N
45 N
____