Question

A shooting star is actually the track of a meteor, typically a small chunk of debris from a comet that has entered the earth’s atmosphere. As the drag force slows the meteor down, its kinetic energy is converted to thermal energy, leaving a glowing trail across the sky. A typical meteor has a surprisingly small mass, but what it lacks in size it makes up for in speed. Assume that a meteor has a mass of 1.5 g and is moving at an impressive 50 km/s, both typical values.

a. Provide an equation for conservation of energy.

b. What is the change in kinetic energy?

c. They say that we can ignore the potential energy for this kind of calculations. What is ΔUg if the meteor travels a vertical distance of 1000 km? Use g = 8.0 m/s. Compare that with ΔK.

d. What is the change in thermal energy?

e. What power is generated if the meteor slows down over a typical 2.1 s? Can you see how this tiny object can make a glowing trail that can be seen hundreds of kilometers away?

Answer 1

conservation of energy means

note that energy is never lost. It just changes form.

In this case, the motion energy called as kinetic energy is converted to heat through friction with atmosphere.

change in kinetic energy = thermal energy generated

________

b)

change in kinetic energy = final energy - initial energy

_________

c)

U = mgh

U = 1.5e-3 * 8 * 1000e3

U = 12000 J

_________

d)

thermal energy = K.E

E = 1/2 * 1.5e-3 * 50000²

E = 1875000 J

______________

e)

power = energy / time

power = 1875000 / 2.1

power = 892857.2 watts

yes, we can see the trail