Question

Jessica's weight is 540 Newtons. According to the Third Law, if the Earth pulls on Jessica with a force of 540 N, then Jessica pulls on the Earth with a force of 540 Newtons that acts in the opposite direction. However, if Jessica stumbles while rollerblading, she will fall down to the ground. Explain why this happens

Answer 1

think about the respective masses of her and the earth and ideas relating to conservation of momentum, ie Newton's Second Law.

Also centre of mass of the Jessica-Earth system will remain same when she tumbles, just another way of looking at it.