How do I solve this force problem?

Question

A horizontal force F of 250 N pushes a block having a mass of 30 kg against a vertical wall. The coefficient of static friction between the wall and the block is 0.5. Will the block start moving?

Answer 1

In the vertical direction there are 2 forces acting: the force of friction which is upward, and the weight of the block which is downward. Now let's compute the magnitude of each:

Weight=mass*g=30*9.8=294N.

Force of friction=uN, where u is the coefficient of
friction, and N is the force normal to the wall. Now substitute known values:

Force of friction=0.5*250=125N.

The downward force is greater than the upward force.
I won't say that the block will start moving.. maybe it had already done so and is now down there below as we speak. (I hope you have a good sense of humor.)

Answer 2

I gave this question a thumbs down because it is ambiguous.

However, we can make some assumptions and still work the problem

First, let's assume the block is actually raised above ground level and being pushed against that vertical wall with force Fh = 250 N. In which case, the forces along the wall direction are W, the weight of the block pulling down and Fv, the force of friction acting upward against the weight.

So we have f = ma = W - Fv = mg - kN; where m = 30 kg is the block mass, k = .5 is the coefficient of static friction, N = 250 N normal force on the block, and g = 9.81 m/sec^2 the acceleration due to gravity at Earth's surface.

The point where the block will start to slide is where f > 0 so that it will accelerate at some a > 0 rate. So we are looking for the point where W > Fv or mg > kN. By inspection we see that this occurs when kN is just less than the weight of the block (W).

So the answer is the block will start to move when kN = 125 < mg = 30 X 9.81 ~ 300 pounds. Since 125 < 300 pounds, the block will start to move.

Answer 3

I'm confused by if you're pushing against the wall, or along it. If you're pushing against the wall, then the block will not move, because the 250 N force isn't enough to break the wall and push the block through it. If you pushing along the wall, instead, then the block will indeed move. This is because a friction force acts in proportion to the normal force, and there is no normal force between the wall and the block, since the force acts parallel to the wall, and thus there is no friction to overcome between the wall and block.

Answer 4

I believe the mass of the block (30kg) is of no importance for any object will move regardless of mass when a force is applied..IF there is no resistance (friction). Here the resistance is 0.5 so I assume that 125N will be absorbed in overcoming the static friction and 125N will be left to put the block in motion... moving the wall if no additional resistance is encountered. (i think this is right...?) All objects move at least slightly (even the floor under your feet) when any force is applied until an equal opposite force is returned... stopping further motion. This is actually how the bathroom scales work when you step on it: What you see is the force required to counteract your weight; which is of course the same as your weight.

Answer 5

the block will indeed move if it is horizontal to the ground because the force of friction comes out as 15N.(by the formula coefficient of friction = force of friction/ mass of the body).so applied force 250N. Force to overcome =15N.thus the body will move if kept horizontal. but if the question suggests vertical then no one can break the wall and push the body.thus it will not move by this case but logically it should move.

Answer 6

Solve the Immigration Problem - Force them to serve or get out.? You want to be in MY Marine Corps with that extensive a short in the headset???? Try that again. I began my service as the last of the Nam era draftees was getting out. They were UNMOTIVATED, prone to discipline and legal problems, there many incidents of drug use and those were Americans in THEIR military. It would be a cold day in HELL before I would advocate the US Military allow any illegals onto any military installation... well one exception: Load the Illegal Aliens onto C-130s and doing a training mission to the most REMOTE airfields in PERU to drop off these idiots with some MREs and 1 liter of water.... (Hike back now, BITCHY-POO!!!) BTW, I thought that we have until King Obama too the con, were meeting our recruiting goals? Am I wrong? edit: Oh I already KNEW that LEGAL immigrants, but not illegals, may enlist in the US Military. Legal Immigrants I have no problem with. I guess that you have a problem since once upon a time you ancestors, along with some of mine, impacted America and her original native Americans. You and I are descendants of Immigrants. So I guess they are here to stay, the LEGALS - anyways.

Answer 7

no. the block wont move. this is because whatever force you apply will lead to a equal magnitude and opp. direction reaction force from the wall. thus the block wont move.

assumption: the wall and the block are both rigid

Answer 8

Hi there,

Yes it will move.

As

Net Force in Horizontal Direction (( 250 -250 )) == 0
Net force in Vertical Direction ( [0.5][250] - [30][9.8] )) == Non Zero


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Answer 9

By force!

Only the block we be impressed.

Th

Answer 10

No. I've tried this.