**Guide :High School **

# A 4 kg book and a 7 kg lamp are both in the living room. If the force of gravity between them is 2.99x10^-10 N. How far apart are they? A. 1.8 m B. 6.3 m

A 4 kg book and a 7 kg lamp are both in the living room. If the force of gravity between them is 2.99x10^-10 N. How far apart are they? A. 1.8 m B. 6.3 m C. 2.1 m D. 2.5 m**Force of gravity = 'G' (mass₁)(mass₂) / (distance)²'G' is the gravitational constant for SI units = 6.67 x10⁻¹¹ newton-meter²/kg²You said that the force is 2.99 x 10⁻¹⁰ = (6.67x10⁻¹¹) (4) (7) / D²Multiply each side by D² : 2.99 x 10⁻¹⁰ D² = (6.67x10⁻¹¹) (28)Divide each side by 2.99 x 10⁻¹⁰ : D² = (28) (6.67 x10⁻¹¹) / (2.99 x 10⁻¹⁰)Take the square root of each side: D = square root of all thatStuff it through my calculator: D = square root of [ (28) (6.67 x10⁻¹¹) / (2.99 x 10⁻¹⁰) ] = √ ( 6.2462...) meters² = 2.5 meters (rounded)===================To get the feel:-- The book weighs about 8.8 pounds (big book)-- The lamp weighs about 15.4 pounds-- They're about 8.2 feet apart.-- The strength of the gravitational force between them is about 0.000 000 001 075 of an ounce .**...