Which of the following is an example of a contact force?

a. a magnet moving a metal object
b. gravity causing a rock to move
c. a person pushing a box across the floor
d. a person falling out of the sky

He table below gives the atomic mass and relative abundance values for the three isotopes of element m. relative abundance (%) atomic mass (amu) 78.99 23.9850 10.00 24.9858 11.01 25.9826 what is the average atomic mass (in amu) of element m? 2.86 5.36 24.30 24.98