Two asteroids in outer space collide, and stick together. The mass of each asteroid, and the velocity of each asteroid before the impact, are known. To find the momentum of the stuck-together asteroids after the impact, what approach would be useful? Use the momentum principle. Use the relationship between velocity, displacement, and time. It depends on whether the collision was elastic or inelastic. Use the energy principle. It depends on whether or not the speed of the asteroids was near the speed of light. Additional Materials

If two asteroids in outer space collide, and stick together and the mass of each asteroid, and the velocity of each asteroid before the impact, are known then the approach that will be useful in analysing this collision is using the law of conservation of momentum which states that the sum of momentum of bodies before collision is equal to the sum of momentum of the bodies after collision. The bodies moves with the same velocity after collision

Let m1 and m2 be the masses of the asteroid

u1 and u2 be their velocity before collision

v be their common velocity

Since momentum = mass × velocity

The relationship that can be used to analyse the approach is;

m1u1 + m2u2 = (m1+m2)v

Note that even though the collision is elastic, the law of conservation will still be used. As a matter of fact this approach can be used if the collision is either elastic or inelastic.