Question

Известно, что чем больше скорость движения молекул тела, тем выше его температура. почему же не нагревается пуля, выстреленная в тире из ружья, хотя все ее молекулы движутся к мишени с большой скоростью?

Answer 1

Молекулы "тела" пули создают трение о воздух, как ни странно. Трение и есть нагрев.

Answer 2

Why doesn't a bullet heat up when fired from a gun, even though all its molecules are moving towards the target at high speed?

The fact that the speed of molecular motion affects the temperature of an object is true in general. However, when it comes to a bullet fired from a gun, there are several factors at play that prevent it from heating up significantly.

1. Time of contact: When a bullet is fired from a gun, it moves at an extremely high velocity towards the target. However, the time of contact between the bullet and the air or the barrel of the gun is very short. This short contact time limits the transfer of heat from the bullet to its surroundings.

2. Heat capacity: The heat capacity of a bullet, which is a measure of its ability to absorb heat, is relatively low compared to other materials. This means that even if there is some transfer of heat during the short contact time, the bullet's temperature does not increase significantly.

3. Heat dissipation: The shape and material of the bullet also play a role in preventing it from heating up. Bullets are typically made of materials with high thermal conductivity, such as lead or copper. This allows heat to be quickly dissipated throughout the bullet, preventing localized heating.

4. Friction and air resistance: As the bullet moves through the air, it experiences friction and air resistance, which can generate some heat. However, the amount of heat generated in this way is relatively small compared to the kinetic energy of the bullet.

In summary, while the molecules of a bullet are indeed moving towards the target at high speed, the short contact time, low heat capacity, heat dissipation, and other factors prevent the bullet from heating up significantly.