Anonymous
Anonymous asked in Science & MathematicsPhysics · 9 years ago

Please help! I have the right answer but i just need to know how to work them out?

1. Masses are distributed in the x,y-plane as follows:6.0 kg at (0.0,0.0) m, 4.0 kg at (2.0,0.0) m, and 5.0 kg at (2.0, 3.0) m. What is the x-coordinate of the center of gravity of this system of masses?

Answer: 1.2 m

2.Tasha has mass 20 kg and wants to use a 4.0-m board of mass 10 kg as a seesaw. Her friends are busy, so tasha seesaws by herself by putting the support at the system's center of gravity when she sits on one end of the board. How far is she from the support point?

Answer: 0.67 m

3. A woman who weighs 500 N stands on an 8.0-m-long board that weighs 100 N. The board is supported at each end. The support force at the right end is 3 times the support force at the left end. How far from the right end is the woman standing?

Answer: 1.6 m

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  • 9 years ago
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    1. You find center of mass by doing (m1 * x1 + m2 * x2 + m3 * x3)/(m1 + m2 + m3). Plug in the numbers. Same thing for the y and z coordinates if you were asked for them.

    2. Decide where you want to put x = 0. You could put it in the middle (then Tasha is at x = 5) or at Tasha's end (then Tasha is at x = 0) or at the far end (then Tasha is at x = 10). The center of mass of the board is in the middle. Depending on where you put x = 0, that will set the coordinate of the middle.

    Then use a formula as above but with only two masses: (m1 * x1 + m2 * x2)/(m1 + m2)

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