AP Physics 2 : Nuclear Forces and Interactions

Study concepts, example questions & explanations for AP Physics 2

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Example Questions

Example Question #1 : Nuclear Forces And Interactions

Which of the fundamental forces is responsible for holding neutrons and protons together in the nucleus of an atom?

Possible Answers:

The electromagnetic force

The strong nuclear force

The weak nuclear force


The intermediate nuclear force

Correct answer:

The strong nuclear force


First of all, the intermediate nuclear force isn't a real force.

Gravity is not responsible for this, because on the scale of quantum mechanical phenomena, gravity has negligible effect, and can be disregarded.

The electromagnetic force doesn't hold the nucleus together, and is actually trying to rip it apart, due to the fact that like charges repel and the nucleus is full of like charges (protons). Accordingly, the force that actually is responsible for holding it together must necessarily be significantly more powerful compared to the electromagnetic force to resist the intrinsic repelling the protons have towards each other.

The weak nuclear force operates on leptons and quarks, and is involved in many of the radioactive decays in nuclear physics, such as beta decay, where a proton decays into a neutron, where it was first revealed.

Since the other three valid forces aren't responsible, that leaves the strong nuclear force. It is the strongest of the four fundamental forces, as it prevents protons from flying away from each other due to their proximity and charge. The strong force mediates over the quarks that make up the protons and neutrons.

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