You are conducting an experiment inside a train car that may move along level rail tracks. a load is hung from the ceiling on a string. the load is not swinging, and the string is observed to make a constant angle of 45∘ with the horizontal. no forces other than tension and gravity are acting on the load. which of the following statements are correct?
check all that apply.
a. the train is an inertial frame of reference
b. the train is not an inertial frame of reference
c. the train may be instantaneously at rest
d. the train may be moving at a constant speed in a straight line
e. the train may be moving at a constant speed in a circle
f. the train must be speeding up
g. the train must be slowing down
h. the train must be accelerating

Newton's second law allows finding the correct answers for the experiment of a body hanging inside a train car are:

         b. The train is not an inertial frame of reference.

          e. The train may be moving at a constant speed in a circle.

          f. The train must be speeding up.

         g. The train must be slowing down.

         h. The train must be accelerating.

Newton's second law says that the net force is proportional to the producer of mass times the acceleration of the body.

A reference system is a coordinate system against which all forces are measured. Newton's second law divides reference systems into two types:

In the attached we have a free body diagram of the system which is a schematic of the applied forces.

In the case indicated, the body is in equilibrium with the weight and tension of the string, therefore there is a component of the force in the x-axis that is not zero. As we are inside the wagon, we do not know if the train is quiet or moving.

Now we can analyze the different responses:

a. False. There is an unbalanced force and with the system in equilibrium, Newton's second law is not fulfilled.

b. True. There is an unbalanced force, therefore the reference system must be accelerated.

c. False. If the train was at rest the body should be vertical.

d. False. If the train is at constant speed, there should be no force on the body  and it would be vertical.

e. True. When moving in a circle there is an acceleration directed towards the center of the circle.

F. True. If the train is accelerating, it is fulfilled.

             Tₓ = m a

  Therefore the body is backwards at an angle of 45º

g. True. If the train is stopping there is a negative acceleration, the body is forward with an angle of 45º

h. True. If there is an acceleration the body deviates from the vertical.

In conclusion using Newton's second law we can find the correct answers for experiment inside to the wagon are:

        b. The train is not an inertial frame of reference.

         e. The train may be moving at a constant speed in a circle.

         f. The train must be speeding up.

        g. The train must be slowing down.

        h. The train must be accelerating.

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b.

c.

e.

h.

Explanation:

If we consider the ball,the tension is not balance by weight then the force acting will be non zero.It means that train car in not inertial frame of reference.And the same time the train car must accelerated with respected to the earth.It is not moving straight path.When train is in rest position but the string will be at the constant angle.

So the following option are correct:

b.

c.

e.

h.

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if the thermos has a vacuum innner, then heat through conv currents and conduction are reduced = vacuum flask