📚 Learning Guide
Energy and Uncertainty in Quantum Mechanics
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If a particle's position is precisely known, what is the most direct consequence on its momentum according to quantum mechanics?

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Choose the Best Answer

A

Its momentum becomes completely certain and predictable.

B

Its momentum becomes highly uncertain and difficult to measure.

C

Its momentum increases indefinitely.

D

Its momentum remains constant regardless of position.

Understanding the Answer

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Answer

If a particle’s position is known exactly, the uncertainty in its position Δx is essentially zero. According to the Heisenberg uncertainty principle, Δx Δp ≥ ħ/2, so when Δx approaches zero the product forces Δp to become very large. This means the particle’s momentum is completely uncertain, spanning an infinite range of possible values. For example, if you pinpoint a particle’s location to a single point on a screen, its momentum could be anything from negative to positive infinity, making it impossible to predict its motion. Thus, knowing a particle’s position precisely destroys any useful knowledge of its momentum.

Detailed Explanation

When a particle’s position is measured very accurately, the rules of quantum mechanics say that its momentum becomes very hard to pin down. Other options are incorrect because Some people think that knowing a particle’s exact spot would let us predict its speed perfectly; A misconception is that making the position very precise forces the momentum to grow without limit.

Key Concepts

Heisenberg Uncertainty Principle
Momentum and Position Measurement
Quantum Mechanics Fundamentals
Topic

Energy and Uncertainty in Quantum Mechanics

Difficulty

medium level question

Cognitive Level

understand

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