Question

practice it! which of the following is not an example of a contact force? opening a door textbook sitting on a desk car accident two magnets repelling each other

Explanation:

Contact forces require physical contact between objects. Opening a door involves hand - door contact, a textbook on a desk has book - desk contact, and a car accident has car - car (or car - object) contact. Magnetic repulsion between two magnets occurs without direct physical contact (it's a non - contact force, a magnetic force acting at a distance).

Answer:

two magnets repelling each other