AP Physics 1: 3.3 Fields in Space

thousand kilometers away from the center of the earth

what's the magnitude of gravitational force that the earth exerts on the

asteroid huh and here the potential answers....... Igor is stressed but we

can't blame him, there's an asteroid out there and he needs to make sure [Asteroid heading towards Earth]

everything stays groovy here on earth now in order to answer this question we

need to remember the formula to figure out gravitational force that equation

goes a little something like this gravitational force is equal to the [Gravitational force equation appears]

gravitational constant G times the mass of the larger object M divided by the

square of the distance between the objects that distance here is the radius

which is shown as R in the equation right there so GM over R squared now the

question doesn't tell us what the mass of the earth is the only number we know

for sure is the distance between the asteroid and the center of the earth

which is 20,000 kilometers so we need to square that number in order to calculate

the gravitational force but wait we need to convert those kilometers into meters

we've got to use standard units because well they're standard for a reason [standard units appear]

20,000 kilometers is 20 million meters and 20 million squared is 400

quadrillion so the correct answer here is D) and boy that's a whole lot of

meters now to answer question like this we need to memorize the equation there's [Boy's head opens and equation appears]

no way around it people now listen carefully...G equals GM over R squared G

equals GM over R squared...... G equals GM over R squared

and now we're starting to understand why scientists go mad