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A) A force of 40N is required to pull a 10kg wooden block at a constant velocity across a smooth glass surface on Earth. what would be required to pull the same wooden block on the planet Jupiter???
Ok first off, it doesnt give the gravity due to accel on Jupiter, and i dont know any formulas. I drew it out and I'm just completely lost.. I looked up Jupiters actual gravity (24.5m/s^2) and used f=mg to find 245N. and then i set up a proportion, you know how 98 over 40 = 245 over x. that got me close to the answer but how do you actually find it the right way?

B) Use G(m1)(m2) over d^2 (newtons version of keplers 3rd law) to find the mass of the earth. the moon is 3.9e8m away from the earth and the moons period is 27.33 days. okay i dont have the mass of the moon and what does all of that have to do with the formula they told me??

C) the asteroid ceres has a mass of 7e20 kg and a radius of 500km. whats g on the surface? what formula do i use!? none of them help me with it!

2007-12-02 09:07:28 · 1 answers · asked by E 2 in Science & Mathematics Physics

1 answers

The acceleration of gravity near the surface of any planet can be computed using Newton's Law of Gravity

g = G M / r^2

where G is the Newton Gravity Constant, M the mass of whatever planet you're interested in, and r the radius of that planet.

It looks like on (A) they want you to realize that the friction force is umg = ( coefficient of kinetic friction ) ( weight ). Near the surface of Jupiter, the acceleration of gravity ( and thus the weight ) would be different.

For (B), you don't need to know the mass of the moon. The centripetal acceleration of the moon α is r ω^2 where r is the distance from the Earth to the Moon (given) and the angular velocity is 2π radians / 27.33 days. Convert days into seconds, find the angular velocity, and then find the force. That force is provided by the gravity of the Earth, so solve

G Me / r = α

for Me, the mass of the Earth.

(C) is again a straightforward application of Newton's Law of Gravity; plug in the mass and radius and solve for the acceleration using the equation at the top of this answer.

2007-12-02 09:16:22 · answer #1 · answered by jgoulden 7 · 0 0

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