2 Friction in starting fires a If you press a wooden peg aga

2. Friction in starting fires

a. If you press a wooden peg against another piece of wood and spin the peg rapidly, it can become hot enough to ignite. The peg produces thermal energy no matter how fast it spins, so why is it important that it spin rapidly?

b. If you strike a piece of flint against a piece of steel, you can shave a red-hot spark off the steel. However, moments later the surface of the steel itself barely feels warm. What happens to the thermal energy in that surface?

c. When you rub a match on a matchbook, it suddenly bursts into flames. The principal source of heat here is a chemical reaction in the match head. What purpose does the initial thermal energy serve in starting this reaction?

d. What is a safety match? How does it work?

e. You might see a “cowboy match” in a movie light a match by rubbing it on the heel of their boot. How does a match light that way.

Solution

(a) It is important to spin rapidly because the thermal energy depends upon the kinetic energy so rapid it move higher is the kinetic energy thus more thermal energy will produce.

(b) The thermal energy in that surface will be go out to the atmosphere.

(c) The initial thermal energy serve provides the activation energy to reaction to occur.

(d) Safety matches are \'safe\' because they don\'t spontaneously combust. You have to strike them against a special surface in order to get them to ignite. The match heads contain sulfur (sometimes antimony III sulfide) and oxidizing agents (usually potassium chlorate), with powdered glass, colorants, fillers, and a binder made of glue and starch. The striking surface consists of powdered glass or silica (sand), red phosphorus, binder, and filler.

(e) By rubbing it with heel of their boot provides it the activation energy for the reaction to occur.