Science Buddies: "Ask an Expert"

Hi, I am taking a Physics 111 and need to build a car with a launching apparataus. The car needs to carry 500 grams and be launched from a free standing launching apparataus no higher than 20 cm. I think I have everything I need for the car but I am not sure what is the best material for the launcher. Any ideas? Also, is it better to have large or small tires on the car to get the longest distance?

thank you so much for any help you can give.

Hi sugarte,
It would be great if you tell me what is the material of your car. And for the tires I suggest to adopt used CDs. The CDs are light and have a fairly large diameter. I am wondering if there are any other requirement for your launching apparatus. I am thinking to use spring as your launching material.

Hope it helps.

Presumably Physics 111 is a university course with a lab. Not sure we are supposed to be helping in these situations.

Also, is it better to have large or small tires on the car to get the longest distance?

It depends on lots of things and YOU need to break it down into physics problems and decide for yourself in your situation.

Think about one of those Monster trucks with the huge tires. Those things are heavy and they take a lot of torque to turn but their large rolling radius means they roll right over speed bumps.

Think about match box cars with their tiny wheels and crude bearings. Hold one up and spin the wheels and they soon stop because of all the frictional forces.

Apply what you learn by thinking about these extremes and come up with to something in between.