1. The Phenomenon
A toy car launcher works as follows:

There is a compressible spring that is attached to a horizontalrail, on which a toy car can roll. The toy car can be pushed backagainst the spring, compressing it a certain distance. There is alittle hook that holds the car against the compressed spring. Whenthe hook is released, the spring pushes the car out of thelauncher, down the horizontal track.

We want to ask some questions and make somepredictions about different cars as they come out of the launcher.Upon close examination of this launcher, it is noted that the
spring is always compressed the same amount each time a car isloaded into the launcher.
The spring stays put inside the launcher as the car is pushedout.
2. What we want to know or predict

• Do all cars come out of the launcher with the same KE?
• Do all cars come out of the launcher with the same speed?
• If they don’t all have the same speed when they come out, whatparameters cause the difference?
• What do we need to do to get our car to have a higher speedthan our friend’s cars?

3. Create a Particular Model and use it to answer thequestions
Plan what you need to do in your group and how you will proceed. Besystematic.
4. Suggestions:
• Use the Energy-Interaction Model and the Spring-Mass Model.
• Consider what energy systems are involved.
• Note: The car is in contact with the spring while it iscompressed and separates
from the spring just as the spring reaches its equilibrium length.During the time
that the car and spring are together, they behave as a spring-masssystem.
• To simplify the notation, use “d” for the distance the spring iscompressed instead
of “∆x”.

HINT! Chose an interval that includes the moment when the springand car are moving the fastest.