Why is this statement correct? "The rougher the surface the more force need to move an object on it".?
926875
friction is opposing force which opposes motion of body\naccrding to new studies fiction force exists due 2 the molecular interaction (forces)  b/w surface and body \nu can see here that more the roughness more the interacction b/w 2 bodies \nhence more fri. forc. hence more force is required 2 move body
939485
Some objects have a smooth surface and others are rough.
26747
ok.  call the downward translational velocity of the whole thing v.  this means that the tangential velocity at the edge of the poles (at the radius r) is equal to v.  the reason for this is that the strings are wound AROUND THE POLES, so this winding and the condition that the string has to unwrap for the thing to move, sets the angular velocity w = v/r.\n\nnow, if you look at the main wheel part, the angular velocity has to be equal to the angular velocity of the poles, since they are one solid piece.  however, as you note the radius of the wheel R > r.  so, the fact that v / r = w = V / R implies that V > v.  in other words, the motion of the outer edges of the wheel is faster than the motion of the outer edges of the rods.\n\ni think you are getting confused by saying that V is the translational velocity of the wheel.  it's not.  v is the translational velocity of the wheel, and of the rods.  the fact that the string is wound *around the rods* and not around the wheel sets the angular velocity of the whole apparatus equal to v/r.  V, the tangential velocity of the outer edges of the wheel, is much faster than the translational velocity.\n\nthat clear?
118752
The fricional force between an object and a surface is dependent on two things,\nthe coefficient of friction between the two surfaces and the normal force exerted by the surface on the object.\nIf you increase either of these, the frictional force is increased, likewise, if you decrease (or make zero) any of these, the frictional force is less (or zero).
895484
SURFACE AREA INCREASES\n\nIT'S VICE VERSA
62076
A\nB would be for a polished surface,\nC and D are never true (although on a macroscopic scale it can appear that they are).
376523
it depends on the angle of ur effort. lets say there u are trying to move a cart. if u push the way u will push ur mower, one component of ur force will be downwards, thus effectively pushing the cart down and thus increasing the frictional force . but if u pull the cart this force will not be downwards but upwards and hence the frictional force will be reduced. so its better to pull.
654890
The greater the pressure difference, the stronger the pressure gradient, hence the stronger the pressure gradient force.\n\nPressure gradient force is responsible for triggering the initial movement of air, which in turn leads to the development of wind. It is directed from higher to lower pressure at right angles to the equal pressure surfaces, isobars. The closely spaced isobars in a weather chart indicate steep pressure gradients, strong forces, and high winds, while widely spaced isobars indicate gentle pressure gradients, weak forces, and light winds.\n\nBernoulli's Principle............
783617
To give you a simple example...\n\nIf you want to move an object of 200kg it would require a force of 200kg.\n\nIf you use one pulley, it would require half of that force... 100kg\n\nIf you use a second pulley placed after the first one, you are reducing it by half again... and it requires a force of only 50kg\n\nUsing several pulleys is called "block and tackle".
396452
1. reduce the force at which the surfaces press together.\n2. allow one surface to slide on top of a film of air rather than the other surface(a la hovercrafts and air hockey)\n3. reduce the roughness of the surface by polishing or using lube.\n\n***I know... they're more than one way... lol***
972973
well if it weighs 2 N and its being pulled down by 5 N. then theres a total downward force of 7 N, which means the normal force must also be 7N (upward). i think thats what you're asking..
740143
it may be that the speed is so fast that it may have reached the maximum speed.... this could be the maximum limit..\nit's critical by common sense...\ncheck the dictionary, or thesaurus....
760338
There is an intrinsic difference between the 2 statements. I am a mechanical engineer and know that a surface can seem to be smooth and feel like it is when in fact it isn`t. The word "is" is  positive and the word "seems" is subjective so both sentences are correct.
613443
Niuchemist is mostly right and deserves the vote, but there is one correction I would make-heavier molecules don't necessarily have less "kinetic energy", they move more slowly-it is the speed of movement that is the critical thing, not the kinetic energy, which is a product of speed *and* mass.
297454
Not sure where the quote is from, but my guess would be they're talking about computing and graphics processing power.  Takes a lot to make a believable scene.
1187223
Well, a clear question would help. \n\nAre you trying to calculate the power that a certain material can withstand?   Or are you trying to calculate strength?
225230
there are only 2\n\n1 is that you have to apply a force, and 2 is that something has to happen ie. movement