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# physics question....?

5.) A neutron of mass (1.67 x 10^-27)kg and speed (1 x 10^5)m/s collides head on with a stationary deutron of mass (3.34 x 10^-27)kg. The particles do not stick together, and the duetron moves off at (6.67 x 10^4)m/s. What is the speed of the neutron? Is it elastic?

### 1 Answer

- 1 decade agoFavorite Answer
We can write a momentum equation

m1u1 + m2u2 = m1v1 + m2v2

Where m1, m2 are mass of the neutron and deutron respectively, u1, u2 is the initial velocity of the neutron and deutron respectively, and v1 and v2 is the final velocity of the neutron and deutron

1.67 x 10^-27* 1 x 10^5 + 3.34 x 10^-27 *0 = 1.67 x 10^-27 *v1+ 3.34 x 10^-27* 6.67 x 10^4

1.67 x 10^-22 + 0 = 1.67 x 10^-27 *v1 + 2.22778 x 10^-22

1.67 x 10^-22 - 2.22778 x 10^-22 = 1.67 x 10^-27 *v1

-5.5778 x 10^-23 = 1.67 x 10^-27 *v1

v1= -5.5778 x 10^-23/ 1.67 x 10^-27 = -3.34 x 10 ^4 m/s

The negative sign means that the particle travels in the opposite direction.. The collision is also perfectly inelastic so tht no energy is lost during the collison.