How many protons does a rubidium atom have

hypothesising or postulating

the chart show the masses and velocities of two colliding objects that stick together after a collision.

according to the law of conservation of momentum, the momentum of the object after the collision is  

answer

1,500

kg • m/s.

electric field is a function of 1/r^2

yes, the force per unit charge for a point charge is inverse square law.