Calculate the mass number of an atom with 8 protons, 12 neutrons and 10 electrons

Which is not a source of noise pollution? a)airplanes b)acid rain c)machines d)cars

Karen is running forward at a speed of 9 m/s. she tosses her sweaty headband backward at a speed of 20 m/s. the speed of the headband, to the nearest whole number relative to a stationary observer watching karen

A20 cm long spring is attached to a wall. the spring stretches to a length of 22 cm when you pull on it with a force of 100 n. what is the spring constant