- #1

clope023

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**[SOLVED] Kinetic Energy and Velocity**

## Homework Statement

The gravitational pull of the Earth on an object is inversely proportional to the square of the distance of the object from the center of the earth. At the Earth's surface this force is equal to the object's normal weight mg, where g=9.8, and at large distances, the force is zero.

a) If a 50000kg asteroid falls to Earth from a very great distance away, how much kinetic energy will it impart to our planet? You can ignore the effects of the Earth's atmosphere.

Express your answer using two significant figures.

b) What will be its minimum speed as it strikes the Earth's surface?

## Homework Equations

Wtot = 1/2m(v2)^2-1/2m(v1)^2

Wgrav = mg

## The Attempt at a Solution

a) W = mg = (50000kg)(9.8m/s^2) = 4.9 x 10^5 J (wrong)

b) W = 1/2mv^2, v = [tex]\sqrt{2W/m}[/tex] = 4.4 (definetly wrong)

as you can see I tried using the work energy theorem with the given data, but nothing was right, any help is appreciated.