The other 4 kg of mass may have departed the scene
of the fire, in the form of gases and smoke particles.
D. The table pushes up on the vase with the same amount of force as gravity pulling it down.
Answer:
A. 30.7cm
B. 
C. The electric field is directed away from the point of charge
Explanation:
A.

B.
Considering Gauss's law

C. The electric field directed away from the point of charge when the charge is positive.
A line that is falling towards the x axis represents an object that is negatively accelerating, or slowing down. When the line hits the x axis, the object has stopped moving. If the graph continues below the x axis, the object has changed direction and is moving backwards at increasing velocity.