9. What happens to the energy stored in oil when you use it to heat your house?
a. It is used up. b. It is destroyed. c. It is converted to heat
energy. d. It stays exactly the same

The upward force acting on the wing of a airplane in flight is known as the "lift" force. (d)

The answer is 4f======since electrostatic force is given by    we let f be the electrostatic force when  r = 1 m    if we let  denote the electrostatic force when the distance is decreased so that r = 0.5m, then    we established earlier that f = kq₁q₂. therefore    the force will now be 4f.