Mousetraps in Motion
This car really zooms!
Topics: Momentum,
Friction, Simple machines
Have fun while using a mousetrap to convert potential energy into kinetic energy.
Materials List
 Mousetrap – needs
a strong spring
 Car with wheels
and axles from the
RAFT Activity
Rolling
Explorations
 Lever arm material
(stiff tube, thin
stick, thin bamboo
garden pole, or
equal)
 VHS tape or string
 Adhesive tape
 Glue (hot or other)
 Cable/Zip ties
 Paperclip or binder
clip
 Wire cutters
 Pliers
 Masking tape
Assembly
This idea sheet is an extension of the RAFT idea sheet Rolling Explorations.
1. Decide if the car needs to travel the farthest or to be the fastest. A distance car
usually requires a longer lever arm, longer car frame, and larger diameter drive
wheels than a car designed for speed. To maximize acceleration, a speed car
needs a shorter lever arm and, usually, wheels with a greater amount of traction.
2. Create the car frame with the required length and a cutout above the drive axle,
see figures 4 and 5 and the RAFT idea sheet Rolling Explorations for details.
3. Discuss the risks and proper handling procedures when using a mousetrap.
4. To reduce the risk of having a finger pinched by the mousetrap, glue a small piece
of sponge to the mousetrap in the location shown in figure 1. Another method is
to cut away most of the trap wire, as shown in figures 2 and 3.
Figure 2
Figure 1
5. Cover the any sharp points with masking tape.
6. Cut the lever arm material to the desired length (short arm for speed, longer arm
for distance). Use cable ties and/or very strong tape to securely attach the lever
arm to the mousetrap spring, or the cut wire (see figure 3).
Figure 3
This activity can be used
to teach:
 Forces & Motion
(Next Generation
Science Standards:
Middle School,
Physical Science 2-2,
High School, Physical
Science 2-1)
7. Align the mousetrap so that the lever arm is centered lengthwise between the
sides of the car frame (figure 4). When the lever arm is bent back the end of the
lever arm should be located just above the drive axle (figure 5). Securely fasten
the mousetrap to the car frame using glue, strong adhesive tape, or cable ties.
End of lever arm is
above the drive axle
Centered
lengthwise
Figure 4
Written by Jay Gluckman (RAFT)
Drive axle
Figure 5
Copyright 2015, RAFT
8. Measure the distance from the drive axle to the end of the lever arm when the spring is in the relaxed
position, see figure 6. Cut a piece of VHS magnetic tape or string about 10 cm (4”) longer than this length.
For tips on removing the tape from a VHS tape cassette, see the RAFT idea sheet VHS Tape Dissection.
9. Attach the VHS tape to the drive axle using adhesive tape or glue.
10. Tie the free end of the VHS tape to a binder clip or paper clip. (A binder clip works best for a solid lever
arm, while a paperclip works best for a stiff tube lever arm.)
Measure the length from
drive axle to end of lever arm
Figure 6
Hold the end of the lever
arm while attaching the
tape to the lever arm
Figure 7
Figure 8
To Do and Notice
1. Carefully rotate the drive axle until almost all the VHS tape is wrapped around the drive axle. The winding
direction will determine if the car will go forward or backward.
2. Tension the mousetrap’s spring by pushing the lever arm towards the drive axle. Hold the lever arm in place
while attaching the clip to the lever arm, see figure 7. Continue holding the lever arm and/or the drive
wheels/axle in place to keep the tape from unwinding.
3. Set the mousetrap car on a large, smooth, level surface; release the lever arm and drive axle, and watch the
car go! Notice how the mousetrap spring forces the lever arm to angle away from the drive wheels/axle, see
figures 7 and 8.
The Science Behind the Activity
A mousetrap car uses the spring on a mousetrap to store potential energy. The spring on a mousetrap is a torsion
spring in the shape of a coil. If the VHS tape was attached directly to a compressed spring then when the spring
was released the tape would only be pulled a short distance but with a great amount of force. With a lever arm
attached to the spring, the tape-attached point is much farther from the spring’s axis of rotation. When the spring
is released less force is exerted on the tape, but the force is exerted for a longer period of time. The total amount
of energy released by the mousetrap spring is the same in both cases. Not all of the stored energy, however, will
be converted into the motion of the car. Some energy is lost to friction as parts rub together (such as the axles in
the hubs) as well as the friction with the ground and the air as the car moves.
Taking it Further


Measure the amount of force needed to pull a mousetrap car, and then calculate the potential energy of the
mousetrap’s spring. Then, calculate the predicted distance of travel of the mousetrap car, experiment and
compare.
Change the materials and the design of the mousetrap car to increase the speed or the distance traveled.
Web Resources (Visit www.raft.net/raft-idea?isid=533 for more resources!)
Information on designing and building mousetrap cars - http://www.pbs.org/saf/1208/teaching/teaching.htm
Mousetraps in Motion, page 2
Copyright 2015, RAFT