Anyone answer and Explain this MultipleChoice (1 Viewer)

[Nosviper]

Hey these are 2 similar questions from different trials.


(1) An object is in a stable orbit around the earth. Which statement about the force acting on this object is correct

a. Both inertial and gravitational forces act on the object
b. Inertial force is the only force acting on the object
c. Gravitational force is the only force acting on the object
d. There is no net force acting on the object

The answer given is D.. which is my original thought.

Then there is another question pretty much the same but my teacher said a different answer than I thought.

(2) A object in an orbiting spacecraft appears "weightless". Which choice correctly identified the net force acting on the object.

a) zero net force
b) gravitational force
d) inertial force forwards
d) centrifugal force

Can anyone explain these questions. I was under the impression that the gravitaional force perpendicular to direction of motion was balanced out by the orbital velocity which is directed at a tangent to the orbit resulting in a zero net force?

 

[alcalder]

Well, my answer would not be D to question 1, because if there were no net force then the object would be travelling in a straight line at a constant speed and therefore not orbitting the Earth.

The answer to 1. should be:

c. Gravitational force is the only force acting on the object

because there is no such thing as inertial force - it is fictitious.

Once again in 2, there is only gravity acting on the body, but since there is the same gravity acting on the spaceship outside, the spaceship and the person are falling at constant speed towards the Earth but keep missing it. They both travel in a circle.

 

[thehootman]

I agree with alcalder. The object is in orbit - ie circular motion ie constantly changing direction which requires acceleration which means there HAS to be a net force - gravity.