(20 1 1? Hangzhou) The ancestors of human beings drilled wood for fire, which turned a new page for human civilization. One way to drill wood for fire is as shown in the figure, sharpening wood.

(1) The distance a person moves by pulling the drill bow back and forth once.

s′= 2s = 2×0.25m = 0.5m,

The work done by a person to pull the drill bow back and forth to overcome friction;

w = Fs′= 16n×0.5m = 8J;

(2) From the topic, Q absorption = w× 25% = 8 j× 25% = 2 j;

∫Q absorption =cm△t, m=0.25g=0.25× 10-3kg,

The temperature of the walking stick has risen;

△t=Q absorption cm=2J2× 103J/(kg? ℃)×0.25× 10? 3kg? =4℃;

(3) As can be seen from (2), the temperature of the stick increases by 4℃ per second,

Time required to raise the temperature from 260℃ to 20℃ = 240℃;

t = 240℃±4℃= 60s。

Answer: (1) The work done by a person to pull the drill bow back and forth to overcome friction is 8j;

(2) In 65438 0 seconds, the tip temperature of the rod can be increased by 4℃;

(3) It takes about 60s to make the stick burn.