Comic strip hero superman meets an asteroid in outer space and hurls it at 100 m/s. the asteroid is on thousand times more massive than superman is. in the strip, superman is seen at rest after the throw. taking physics into account, what would be his recoil speed?

Recoil speed = -100,000 m/s

Explanation:

First, this is an exercise that has relation with angular momentum.

So, you need to use the expressions for momentum.

Now, we can assume that Superman and the asteroid are initially at rest, so both moments are 0.

If superman hurls the asteroid, this means that  he should have an equal moment but in the opposite direction of the asteroid, therefore, he also have an opposite recoil moment.

The expression to use is the following:

innitial momentum = final momentum

The final momentum, is the combination of superman recoil moment, and the asteroid so:

0 = Mass * Velocity

Let M1 and V1 be the mass and velocity of superman, while M2 and V2 would be the asteroid, thus we have:

0 = M1 * V1 + M2 * V2

As the problem states, the asteroid is 1000 times more massive than superman, so we can say that M2 = 1000M1. Replacing in the above expression we finally have:

0 = M1 * V1 + 1000M1 * V2

M1 * V1 = -1000M1V2 > Simplify M1

V1 = -1000V2

V1 = -1000 * 100

V1 = -100,000 m/s

This would be the recoil speed of Superman.