Chapter 12.  Mr. Newton, whose mass is 60.0 kg, is doing a physics demonstration in the front of the classroom.  A) how much gravitational force does.

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Chapter 12

 Mr. Newton, whose mass is 60.0 kg, is doing a physics demonstration in the front of the classroom.  A) how much gravitational force does he exert on 55.0 kg Martha in the front row, 1.50 m away?  F = G*m 1 *m 2 d 2

 G = 6.67x10 -11 Nm 2 /kg 2  m 1 = 60.0 kg  m 2 = 55.0 kg  d = 1.50 m  F=?

 F = (6.67x10 -11 Nm 2 /kg 2 )(60.0kg)(55.0kg) (1.50m) 2  F = 9.78x10 -8 N

 B) how does this compare to what he exerts on 65.0 kg Lester, 4.00 m away in the back row?

 G = 6.67x10 -11 Nm 2 /kg 2  m 1 = 60.0 kg  m 2 = 65.0 kg  d = 4.00 m  F=?

 F = (6.67x10 -11 Nm 2 /kg 2 )(60.0kg)(65.0kg) (4.00m) 2  F = 1.63x10 -8 N

 Our galaxy, the Milky Way, contains approximately 4.0x10 11 stars with an average mass of 2.0x10 30 kg each. How far away is the Milky Way from out nearest neighbor, the Andromeda Galaxy, if Andromeda has an average mass of 8x10 41 kg and attracts the Milky Way with a gravitational force of 2.4x10 30 N?

 G = 6.67x10 -11 Nm 2 /kg 2  m 1 = (2.0x10 30 kg)(4.0x10 11 ) = 8x10 41 kg  m 2 = 8x10 41 kg  F = 2.4x10 30 N  d=?

 d = √G*m 1 *m 2 /F  d= √(6.67x10 -11 )(8x10 41 )(8x10 41 )/(2.4x10 30 )  d = 4.2x10 21 m

 Force= mass * acceleration (gravity)  m * g = G * m 1 * m 2 d 2  One of the masses cancels, left with  g = G * m 2 d 2

 Teresa is standing in the lunch line 6.38x10 6 m from the center of Earth. Earth’s mass is 5.98x10 24 kg.  What is the acceleration due to gravity?

 m 2 =5.98x10 24 kg  d=6.38x10 6 m  G=6.67x10 -11 N*m 2 /kg 2  g=?

 g = G * m 2 d 2  g = (6.67x10 -11 )(5.98x10 24 ) (6.38x10 6 ) 2  g = 9.80 m/s 2

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