Tom Hamlin, age 12, of Nashua, N.H., for his question:

HOW FAST DOES A BOBSLED TRAVEL?

Bobsledding is a competitive winter sport in which teams of two or four descend a steep, icy run on a bobsled. Although racing sleds have been clocked at speeds up to 118 miles per hour they generally average between 60 and 70 miles per hour.

A typical bobsled consists of two small sleds connected by a semiflexibie steel platform. The crew sits on the platform. Steering is accomplished by means of a rope or wheel attached to the front sled.

Most racing sleds are equipped with brakes and have streamlined aluminum cowls mounted on the front ends. The captain of a bobsled team occupies the front position and steers the sled while the person in the rear position operates the brake.

On four member sleds an important function of the two center members is to help "bob" the sled. The three crew members "bob" their vehicle by leaning backward at an extreme angle and then snapping forward in unison. This action, which gives bobsledding its name, sharply accelerates the speed of the sled.

The famous bobsled run at Lake Placid, N.Y., is 1.5 miles long and has an angle of descent ranging form 8.5 to 15 degrees. Some of the 26 turns are more than 30 feet high and have almost vertical ice coated walls.