Jessica Alba's weight is 540 newtons. According to the Third Law, if the Earth pulls on Jessica Alba 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 Alba stumbles while rollerblading, she will fall down to the ground. Explain why this happens.

Question

yadu123 · Answer

is it because of gravity

perl · Answer

yes , jessica falls because of gravity

yadu123 · Answer

thats it?

perl · Answer

well i think the question is asking, why doesn't earth 'fall into' or move towards jessica alba

perl · Answer

if jessica falls towards earth when she is not supported by her rollerblades on the ground, why doesn't earth fall towards jessica? doesn't newtons third law say force comes in reaction pairs

perl · Answer

the answer is, yes the earth does accelerate towards jessica, but because of earth's giant mass, the acceleration is not noticeable, its insignificant

yadu123 · Answer

oh ok

perl · Answer

force = mass * acceleration
540 newtons = earth mass * acceleration

if you divide 540 by earth mass, acceleration will be tiny

yadu123 · Answer

makes total sense now

perl · Answer

but with jessica

540 newtons = jessica's mass * acceleration

dividing 540 by her mass (which is about 54 kg) , that causes 9.8 or about 10 m/s^2 acceleration

yadu123 · Answer

ok