Mass number = no. of protons + no. of neutrons
so, it would be, 3+4 = 7
Answer:
A horse pulls a cart, a person walks on the ground
Explanation:
A. altitude should be correct
Answer:
G M m / R^2 = m v^2 / R gravitational force = centripetal force
G M = v^2 R = constant
As v increases R will must decrease
Take the moon as an example
S = 2 pi R where R is about 240,000 miles for one orbit
S / 1 day = 54,000 miles/day for a 28 day circuit
S / 1 hr = 54000 / 24 = 2200 mph which is much less than a satellite in orbit