1. We designed the car to be lightweight, thus, we used Balsa wood, which is not dense and thus light. This is so that we can reduce the mass and increase the acceleration as the force from the Spring remains the same (F=ma, if m is reduced, a will increase).
2. We designed the back wheel to be larger than the front wheels so that the centre of the gravity will be towards the front. This will cause the car to have a tendency to move forwards after it begins motion. This is due to inertia and because the gravitational force is further downwards than the centre of the car, the car will slide forwards.
3. We chose to add a lever arm instead of just tying the string onto the mousetrap as this would increase the moment about the lever and, therefore, add more force to the car and make it move faster.
4. We decided to use rubber tape around the edge of the CD as it increases the friction between the wooden stick and the CD without compensating its turning ability as the wheels.
Length of string
Length of lever extension