Question

Consider the free body diagram. If the sum of the tension forces is equal to the force of gravity, which description BEST applies?
A) A book is at rest on a tabletop.
B) A physics student rests a backpack upon one shoulder.
C) A girl hangs by both hands, motionless, from a trapeze.
D) A girl falls slowly to Earth while strapped to a parachute.

Answer 1

C.)    A girl hangs by both hands, motionless, from a trapeze.

Answer 2

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.