BR test 1 physical sciences q 33

[2010premed]

According to the data in Table 1, if a single neutron traveling at 1000 m/s from right to left strikes an atom of U-238 to form a new element, then the new isotope has a velocity of:

A:4.2 m/s to the left.

... anyone have a good explanation?

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[phltz]

It's an inelastic collision. Use conservation of momentum. Initially, only the neutron has momentum. p_init = (1 amu)(1000 m/s). At the end, only the isotope has momentum. p_final = (239 amu)(v_final). Setting p_init = p_final, you can solve for v_final.

 

[Baylor2012]

Hoooray!!!!!

 

[2010premed]

Thanks. And how do you know it's an inelastic vs elastic?

 

[phltz]

A perfectly inelastic collision is one in which the two objects completely stick together. Momentum is conserved, but energy is not. We are told that the neutron and nucleus for a new element, which means they've stuck together.

In a perfectly elastic collision, on the other hand, they bounce off of each other, conserving both energy and momentum.

Most real collisions are actually somewhere in between, involving objects that bounce off of each other, conservation of momentum, and some loss of energy.

 

[2010premed]

thx =)

 

[Pons Asinorum]

A perfectly inelastic collision is one in which the two objects completely stick together. Momentum is conserved, but energy is not. We are told that the neutron and nucleus for a new element, which means they've stuck together.

In a perfectly elastic collision, on the other hand, they bounce off of each other, conserving both energy and momentum.

Most real collisions are actually somewhere in between, involving objects that bounce off of each other, conservation of momentum, and some loss of energy.

Energy is conserved; kinetic energy is not conserved. I'm sure if the problem wanted to be evil, it would have asked you to determine the mass defect of the collision or something like that. Just remember that momentum is always conserved, regardless of collision type and you'll be fine.