Question

Which of the following pairs of forces is not a valid example of action and reaction to which Newton's third law of motion applies?
a) The weight of a satellite in orbit around the Earth and the attractive force on the Earth's centre of mass due to the satellite.
b) The forces of repulsion experienced by two parallel wires carrying currents in opposite direction.
c) The forces of attraction felt by two gas molecules passing near to each other.
d) The weight of an object resting on the table and the force acting on the object due to the table supporting it.

Answer 1

Newton's third law is:

For every action, there is an equal and opposite reaction.

Answer 2

So based on that, which option do you think it is?

Answer 3

wow that one is real doozy!

Answer 4

a?

Answer 5

That's a good question! Remember that in the pair of forces, each has to be applied to a DIFFERENT system.

Answer 6

so its d?

Answer 7

why do u think its d?

Answer 8

random guess lol

Answer 9

is it a? since both forces seem to me like they are acting on the earth

Answer 10

"and the attractive force ON THE EARTH'S CENTRE of mass due to the satellite"

Answer 11

it should be attractive force on the satellite due to the earth?

Answer 12

The answer is D. The object is at rest, it has no motion. And I can assure you it's not a. as Just did a gravitation problem yesterday and t

Answer 13

And while there wes force acting upon the book (gravity and normal forces is both directions,, it is not is a there is no net momomemnutm force.

Answer 14

This is so confusing lol

Answer 15

is it d because gravity and the force exerted upwards by the table is acting on the book?

Answer 16

No, it's D because the book is at rest and thus at equilibrium. If you were to push down on the book, or otherwise aid gravity, then the normal force would respond to that action. and NTLoM would apply, but in order for the law to apply, there must be some action and while at rest, there is no action for there to be and equal opposite reaction. The rest involve active interactions where as the rest.

Answer 17

I see, thanks for your help

Answer 18

I see @DerBärJuden helped you answer this question. Did you know you could medal people for helping out? Just click the blue box labeled best response next to his name. :)

Answer 19

Quote: "is it d because gravity and the force exerted upwards by the table is acting on the book?"

Yes! you are right. As both forces act on the book, they cannot belong to an action-reaction pair.