Rigid Bodies and Center of Gravity?
964442
Any point can be chosen as the pivot. I choose the fingers and I choose CCW torque to be negative.\n\nTorque of thumb + tray + food + coffee = 0\n-T*.04 + .16*g*.1 + 1.0*g*.14 + .18*g*.28 = 0\n\nT = g*(.016 + .14 + .05)/.04 = 50.5 Nt\n\nThe fingers have to be providing the upward force at the chosen pivot to keep the whole thing up. So \nF = (.16 + 1.0 + .18)*g = 13.1 Nt
79440
center of gravity \n\nThe point in any solid where a single applied force could support it; the point where the mass of the object is equally balanced. The center of gravity is also called the center of mass. When a man on a ladder leans sideways so far that his center of gravity is no longer over his feet, he begins to fall.
643446
If we assume the Earth is a perfect spehere, the gravitational accleration would, indeed, be equal at any point along the surface of the sphere.\nWhen you take the rotation of the Earth into account, yes, at the equator, an object's "weight" is less than it would be at the poles.\n\nThe gravitational acceleration acts as the centripetal acceleration which keeps us all on on the Earth instead of flying out into space in a straight line.\nAt the poles, no centripetal acceleration is needed (neglecting Earth's revolution around the sun), but at the equation, the objects inertia acts to lessen the appearent effects of gravity and reduce its weight.  This is NOT due to the fictitious centrifuga force.
1076161
An object orbiting another in space can be considered to be in freefall around the center object.  You have probably heard someone explaining circular motion like that of an astronaut or space station or the moon as being in freefall towards the earth.  It's a balancing act between the gravity between the two objects (causing the free fall) and the inertia of the planets, moons, satelites, etc that keep them moving in a direction perpinduclar to the inward falling direction.  \n\nEventualy the orbiting object will have to fall toward the center object or away from it, debending on whether the inertia or the gravity is stronger.  \n\nOur moon is moving away from us.\n\nAll the stars in the galaxy are moving around the center of the galaxy and all the galaxies are moving around the center of the universe but we will never fall in because not only is the universe still expanding, the rate at which all the galaxies are moving away from the center of the universe is getting faster.
12398
The rotational energy you impart to the object when spinning overcomes the force of gravity that would topple a stationary object.  \n\nA total layman's explanation:\n\nA perfect stationary top perfectly balanced will not fall over.  In real life though,it's impossible to perfectly balance a top.  It's shape practically guarantees that its center of gravity will not be directly over the balance point for any practical length of time.  Imperfections in the material will cause a slightly uneven weight distribution, air currents will introduce a small force, and mechanical vibrations will be transmitted through the medium the top rests on.  The upshot of all this is that as soon as the center of mass is no longer over the resting point, gravity is going to pull the top over.  \n\nNow gravity has an acceleration of 32 feet per second squared (if I remember my ancient high school course correctly).  It can only topple the top at a specific speed.  If you spin the top fast enough, any side that gravity tries to "pull down" will translate around so quickly that it literally has no time to fall.  If you were standing on a planet with a much higher gravity, you'd have to spin the top far faster to achieve stability, and if you were on the moon, it would spin for a much longer time. Eventually, however, the top starts to slow and the tip will inscribe little circles.  That action is called "precession".  And of course, eventually the thing drops to the table and the game is all up once it slows enough.\n\nAgain, that's a layman's view of how it works.  Some college physics major is probably going to come in here and make my answer look really foolish.
64466
Yes! There is centripetal acceleration on the ball.  It is actually accelerating in towards the center, but other forces keep it on the edge.
1065224
Motion of a particle can be defined using the following variables- acceleration, velocity ( initial and final) , time elapsed and displacement. Motion can be translatory only for a particle.It includes linear , circular and projectile.\n\nMotion of a rigid body is defined in terms of translatory motion (motion of c. o. m. of the body) plus rotatory motion, which considers the motion of other particles w.r.t. center of mass.
710706
Gravity, friction and centrifigul.  Don't forget various applications of force = leverage, pulleys.
659614
In order to get better responses, you will need to more specific and explain what you mean by that "question".\n\nThe first thing that came to my mind was centripetal force which maintains circular motion.  Without centripetal force, the object would not be in circular motion (thus linear motion).
1093836
Centrifugal force and gravity.
921247
well somewhere in the middle you might become weightless as you would be in the center of a spinning mass. but most likely you would get to a point that the gravity would push you back. just like on a merry go round getting to the center is actually pretty hard.
698221
Silly...  The point your instructor is making is that barring any impeding object (air) in the horizontal(to the ground) velocity vector will remain the same (First Law of Motion).  Of course his use of never is inappropriate.  Any thrown object will eventually fall, go into orbit, or escape earth's gravity and fly into space.  At which point the object might encounter another impeding object...\nI recommend that you suggest to your instructor that he reword the question. (Forget trying to get the point).  Explain to him that Newton's First Law states "An object at rest tends to stay in rest and an object in motion tends to stay in motion in a straight line at constant speed unless acted upon by an outside force."...  Notice Newton himself refrains from the use of NEVER and uses the unless clause.  Explain to the instructor that you were using the UNLESS in the 1st Law.  That is to say he did not tell you to ignore gravity or any other impeding objects.  So, tell the instructor that you now understand what he was asking BUT s/he would be better off either taking out the NEVER (which Newton would not have used) with "until it hits the ground."\n\nAddition:\nGiven the Q as a true/false statement and understnading that the question is asking about Newton's First Law and knowing that even Newton says "nisi quatenus a viribus impressis cogitur statum illum mutare." which means "unless acted upon by an external and unbalanced force."  I would say FALSE! \n(The word "never" should not have been used).
939985
Well, yes, the gavity is pulling you down, and you are not moving. So you are subjected to an acceleration and are not moving.\nMind you, one can argue that the *resulting* force is zero, as the ground is reacting with an equal and opposite force to your weight; if you take it that way, to have an unbalanced force should result in motion.
803150
check out this site for the answer\nhttp://math.ucr.edu/home/baez/physics/Relativity/GR/centre.html
308046
Gravity. A sphere is the shape which allows every part of the planet to be as close as possible to the centre. Planets which spin are flattened slightly, so that they are not exact spheres, the faster the spin the more they are flattened. Earth is slightly flattened at the poles. If a planet was not a sphere, the parts which stuck out further than average would effectively be "mountans" and any loose parts would roll down under gravity, thus the planet becomes more spherical
335564
The center of gravity will be different for different people depending on their height or weight or if the have their arm pointing forward or backward etc.  When you stand up from the sitting position all you are doing is changing where your center of gravity is to make it easier to stand.  Speed does not effect center of gravity however acceleration and deceleration does.
688313
Are you sitting down? Yes? Good. You are experiencing a force which is opposing gravity. The Earth's gravity is pulling down on your mass (i.e., weight = mass * gravity) and the chair that you're sitting on is pushing up on your butt with a force equal in magnitude to the gravity pulling down on you and in the opposite direction. The sum of the forces acting upon you is 0. (You could also just look at the equation F = m*a and say, "Well, I'm not accelerating, and I know that my mass is non-zero. Therefore, the total force acting upon me is 0. If that is true, and I know that gravity is always pulling down on me, there must be an equal and opposite force(s) acting upon me.")\n\nIf it's anti-gravity that you're asking about on the other hand... it doesn't exist. Stop watching Star Trek and start reading real physics books.\n\nAs for the comments about "NASA" in the answer above... this is exactly wrong. By letting the plane drop, they make it so that the ONLY force acting upon the subjects is gravity. The only thing that has gone away is the floor of the plane beneath the subjects, allowing them to "free fall" inside the plane. The occupants only "appear" weightless with respect to the reference frame of the spacecraft when in orbit about a planet. Gravity is ALWAYS acting upon both the spacecraft and its occupants. What happens is that the spacecraft and its occupants are both falling at the same rate. Gravity is what keeps it in the orbit and keeps it from floating off into space. You would have to be infinitely far away from the planet in order for the force of gravity to be zero.