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PhysicsModern PhysicsNuclear physicsHard2 minQB

PhysicsHardnumerical

Passage / Comprehension

When an $α$ - particle with kinetic energy $K = 14 MeV$ collides with a stationary lithium nucleus, the following nuclear takes paces.

$^{4} He +^{7} Li \to^{10} B + n$

The Q-values of this reactions is $E = - 2.9 MeV$ and the neutron is outgoing at right angle to the incoming direction of the $α$ -particle. If kinetic energy of the neutron and the boron nucleus are $K_{1} MeV$ and $K_{2} MeV$ respectively.

The value of $K_{1}$ is $____$

Answer:

5.00

Solution:

Momentum (neutron ⊥ α): $10 K_{2} = 4 K + K_{1}$ , so $10 K_{2} - K_{1} = 56$

Energy: $K_{1} + K_{2} = 14 - 2.9 = 11.1$

Solving: $11 K_{2} = 67.1$ , $K_{2} = 6.1$ MeV, $K_{1} = 5.0$ MeV

Answer 5.00

Stream:JEESubject:PhysicsTopic:Modern PhysicsSubtopic:Nuclear physics

⏱ 2mℹ️ Source: QB

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