# The drawing (not to scale) shows one alignment of the sun, earth, and moon. The gravitational force Fsm that the sun exerts on the moon is perpendicular to the force Fem that the earth exerts on the moon. The masses are: mass of sun = 1.99 × 10^30 kg, mass of earth = 5.98 × 10^24 kg, mass of moon = 7.35 × 10^22 kg. The distances shown in the drawing are rSM = 1.50 × 10^11 m and rEM = 1.50 × 108 m. Determine the magnitude of the net gravitational force on the moon.

I've got an estimated answer as 1.4 x 10^21N, which is my net force.

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1. use the universal gravitation formula to find the individual forces

add the two vectors to find the net force

the data looks like three sig fig ... so your answer should be also

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2. when adding numbers written in sig figures, remember you can only add to the least sig figure in the largest number: ie 10200+34=10200, in that case a three sig figure plus a two sig figure yields a three sig. Example 2: 1020000+3433=102000, a three sig plus a four sig gives a three sig. So when adding vectors, watch this . Often we get bambluzoled when adding because of the cosine, sin conversion to get components makes us think each has more precison that it actually has.

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bobpursley