Answer:
C) A girl hangs by both hands, motionless, from a trapeze.
Explanation:
The free body diagram in the figure gives us several pieces of information:
- There are two forces upward and one force downward. --> these could correspond to the forces of the two harms of the girl (upward) and the weight of the girl (downward)
- The sum of the tension forcs is equal to the force gravity --> this tells us that the net force is zero, therefore this could corresponds to the girl hanging motionless from the trapeze.
Let's see why the other options are not acceptable:
A) A book is at rest on a tabletop. --> In this case we would only one have one force downward (the force of gravity) and one force upward (the normal reaction of the tabletop)
B) A physics student rests a backpack upon one shoulder. --> this does not corresponds to two forces upward and one force downward
D) A girl falls slowly to Earth while strapped to a parachute. --> Again, in this case we would have one force downward (force of gravity) and one force upward (the air resistance on the parachute)
So, the only possible option is C.
