Calculate Time to Move 2 Isolated Masses: Gravitational Field

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Two isolated masses, M1 = 2.20 kg and M2 = 607 kg are initially rest, a distance d = 171 cm apart. Their gravitational attraction is the only force acting. Calculate the time it takes for M1 to move from that distance to 169 cm from M2. Assume that M2 does not move and that the force is constant over that small distance, and equal to that at 170 cm.

i want to use F=G(m1m2)/r^2=m1a so Gm2/r^2=a

6.67x10^-11*607/(1.71/2)^2=a

then when i have a i am going to use x=xo+volt+.5at^2 to find t

i am not getting the right answer please help me
 
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Actually, I think I will stick with my original advice. Like I said, you shouldn't be dividing the distance by 2. If the force is constant, I would think you take it at the 1.71 m.
 
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At a blush. I think the decision to halve the 171 is mistaken
 
Obviously you are supposed to consider that the acceleration is constant, or else you would have to deal with some differential equations.
 
well the problem tells you to use 170,
so we have :
f=6.67E-11*607*2.2/.170^2=?

Divide by 2.2 to get a, then use kinematics

PS oops that's meant to be 1.7
 
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