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2 physics multiple choice questions

I am stuck on these two questions. thanks in advanced!

1. Which of the following is an inertial frame of reference?


a) a child on a moving swing observes the child next to them moving in sync
b) a child on a moving swing observes a ball that they throw to their parents standing on the ground
c) a child observes the motion of the planets in the night sky over many nights
d) a child observes the motion of the sun across the sky during the day


2. In a pulley problem involving an inclined plane:


a) the gravity need to be resolved into components
b) the tension need to be resolved into components
c) the friction need to be resolved into components
d) the direction convention is the same for both blocks
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Original post by waterhouse
I am stuck on these two questions. thanks in advanced!

1. Which of the following is an inertial frame of reference?


a) a child on a moving swing observes the child next to them moving in sync
b) a child on a moving swing observes a ball that they throw to their parents standing on the ground
c) a child observes the motion of the planets in the night sky over many nights
d) a child observes the motion of the sun across the sky during the day


2. In a pulley problem involving an inclined plane:


a) the gravity need to be resolved into components
b) the tension need to be resolved into components
c) the friction need to be resolved into components
d) the direction convention is the same for both blocks




1 is a because that is the only one where there is no acceleration relative to the object being observed. in a the acceleration of both children is the same at all points. whereas in b, the is an acceleration of the child on the swing and on the ball which are not equal, in c, earth has a different acceleration to the other planets, and d there is an acceleration due to the circular orbit of earth which is not the same for the sun.

2 i am not so sure on. I would assume it is a. It is definitely not c as friction only acts along a plane. b and d depends on what is being calculated and how the apparatus is set up but doesnt have to be true. for d, direction of convention is only the same if the whole system is being considered. if parts are considered separately then they can be different. and a, weight needs to be resolved, however gravity isnt a force so isnt resolved which is why it confused me. i would guess a, but i could be wrong

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