A steel ball hangs from a thread near a magnet. The magnet does not touch the ball. The table lists three interactions.
| Interaction | Objects involved |
|---|---|
| P | Thread and ball |
| Q | Magnet and ball |
| R | Earth and ball |
Which classification is correct?
P is contact; Q and R are non-contact.
Q is contact; P and R are non-contact.
P and Q are contact; R is non-contact.
P and R are contact; Q is non-contact.