Imagine that space invaders could deposit extra electrons in equal amounts on th
ID: 2159742 • Letter: I
Question
Imagine that space invaders could deposit extra electrons in equal amounts on the Earth and on your car, which has a mass of 1250 kg. Note that the rubber tires would provide some insulation. How much charge Q would need to be placed on your car (same amount on the Earth) in order to levitate it (overcome gravity)? [Hint: Assume that the Earth's charge is spread uniformly so it acts as if it were located at the Earth's center, and then the separation distance is the radius of the Earth.]_______________________C
Explanation / Answer
Weight of car is W = 1250 x 9.8 in Newtons earth radius 6,371,000 m Coulomb's law, force of attraction/repulsion F = Q1Q2/(4pe0r²) where e0 = 8.8542e-12 F/m = permittivity of space (Farad/meter) Q is charge in coulombs r is separation in meters apply the above equation, substituting Q² for the two charges and solving for Q F is the weight of the car.