Which is a good example of a contact force?

protons in the nucleus of an atom

a ball falling down after it's thrown up into the air

a satellite orbiting earth

a bat hitting a ball

i think it’s a. this is because if they measured the mass of something with a mass of 150g, then their final answer would have to be approximately 150g. though all of their answers are almost 150, rosa and tran have the closest answers (or the exact answer) to the accurate one.

find the sum of the two horizontal vectors and the sum of the two vertical vectors

isoceles right angled triangle