when two objects are in contact, moving together, which of the following statements must be true? choose all that apply.

When two objects are in contact and move together (i.e., they share the same motion), the following statements must be true:

1. They exert the same magnitude force on each other.
   • By Newton’s third law, any interaction between two objects involves equal and opposite forces.
   • So, if object A pushes on object B, object B pushes back on object A with the same magnitude force in the opposite direction.
2. They have the same acceleration.
   • If the objects are “moving together” (for example, a box resting on a cart and both speeding up along the floor), their positions relative to each other do not change.
   • That only happens if their accelerations are equal; otherwise, one would pull ahead or lag behind.
3. What is not necessarily true:
   • They do not need to have the same net force on them.
     • Net force depends on both interaction forces and all other forces (like gravity, normal force, friction).
     • If their masses differ, equal acceleration requires different net forces Fnet=maF_{\text{net}}=maFnet​=ma.
   • They do not need to have the same weight.
     • Weight depends on mass and gravity; two contacting objects can certainly have different masses and therefore different weights.

So, from a typical multiple-choice list like:

• The objects must exert the same magnitude force on each other.
• The objects must have the same net force acting on them.
• The objects must have the same acceleration.
• The objects must have the same weight.

The statements that must be true are:

• “The objects must exert the same magnitude force on each other.”
• “The objects must have the same acceleration.”