# Physics question on forces.

#1
I'm confused on what to write for a physics question:
Context:
Diagram shows a brick on a table with equal forces acting upwards and downwards, 2 times more friction forces than a pushing force which is being exerted on the brick in the opposite direction.

The pushing force does not make the brick move as there is not enough power being exerted.(Is this right?)

The weight of the brick does not make it move downwards through the table as the force of the weight of the brick is directly proportional to the upwards force of the table, making the resultant force 0N, (Is this right?)

A bigger pushing force does make the brick slide across the table. Write down one thing that the sliding brick will do to the surface of the table.
What does it do?
0
8 years ago
#2
What are you exactly confused on? Is there a diagram you could upload?

Every force has an equal but opposite reaction, the forces are balanced out on the brick.
Weight (mg) acts downwards from the brick but the normal contact force from the table is acting upwards therefore resultant force is 0N (equilibrium).

You know the direction of the force is based upon the resultant force, so if you were to push the brick horizontally across the table it would travel horizontally.
And as for what it will do to the table I think because of its material, dependant on the tables material also.

What you've written is correct but be sure to use key terms, hope I helped
0
8 years ago
#3
Seems like a vague question to be honest, do you have a picture of the full questions?

One thing that would happen to the table is that the temperature of the table will slightly increase due to vibration of particles caused by the brick overcoming the static forces
0
8 years ago
#4
From your description, you are correct, if the Force of Friction is larger than that of the Force trying to get the object to move, we can say with general certainty that the brick is not moving.
Next, you are correct in saying that the brick will not go through the table because of the upwards force from the table, and thus the Earth, this is a Newton Pair from Newtons Third Law of Motion.
Finally, the block will heat up the table. We know that the table is applying a force of friction in one direction and we know that the brick is overcoming this friction, therefore there will be a build up of heat, all be it it will be tiny. You might be able to see this better of when a car is driving along a road, (the speed and size is much greater however) this might give you somewhat of an example.

Hope that helps.
0
8 years ago
#5
(Original post by Zaros)
From your description, you are correct, if the Force of Friction is larger than that of the Force trying to get the object to move, we can say with general certainty that the brick is not moving.
Next, you are correct in saying that the brick will not go through the table because of the upwards force from the table, and thus the Earth, this is a Newton Pair from Newtons Third Law of Motion.
Finally, the block will heat up the table. We know that the table is applying a force of friction in one direction and we know that the brick is overcoming this friction, therefore there will be a build up of heat, all be it it will be tiny. You might be able to see this better of when a car is driving along a road, (the speed and size is much greater however) this might give you somewhat of an example.

Hope that helps.
If the force of friction (opposing force) is greater than the force pushing the object forward then the object will not be stationary. It will be moving in a backwards direction. For the object to be stationary, the force of friction (opposing force) must be equal to the force pushing the object.
0
8 years ago
#6
(Original post by Revolutionizer)
I'm confused on what to write for a physics question:
Context:
Diagram shows a brick on a table with equal forces acting upwards and downwards, 2 times more friction forces than a pushing force which is being exerted on the brick in the opposite direction.

The pushing force does not make the brick move as there is not enough power being exerted.(Is this right?)

The weight of the brick does not make it move downwards through the table as the force of the weight of the brick is directly proportional to the upwards force of the table, making the resultant force 0N, (Is this right?)

A bigger pushing force does make the brick slide across the table. Write down one thing that the sliding brick will do to the surface of the table.
What does it do?
The diversity of answers in this thread , some right and some wrong, is due to the fact that the question has not been correctly posted.

Please post the original question in full. Including the diagram.

For example, what does "...2 times more friction forces than a pushing force..." mean?
0
8 years ago
#7
(Original post by ImNormal)
If the force of friction (opposing force) is greater than the force pushing the object forward then the object will not be stationary. It will be moving in a backwards direction. For the object to be stationary, the force of friction (opposing force) must be equal to the force pushing the object.
You are actually wrong. Frictional force is created by two different materials rubbing together. If you have a large frictional force it will not push the object backwards. For example, if I have a car traveling on a piece of sandpaper (I have no idea how or why) if the frictional force going against the car is greater than the car pushing forward, the sandpaper wont magically push the car backwards...
0
8 years ago
#8
(Original post by Zaros)
You are actually wrong. Frictional force is created by two different materials rubbing together. If you have a large frictional force it will not push the object backwards. For example, if I have a car traveling on a piece of sandpaper (I have no idea how or why) if the frictional force going against the car is greater than the car pushing forward, the sandpaper wont magically push the car backwards...
If that's the case, then it'd either be the maximum friction force (which would increase over time but never exceed the forward force) or the coefficient of friction between the object and the surface.

Posted from TSR Mobile
0
8 years ago
#9
(Original post by Zaros)
You are actually wrong. Frictional force is created by two different materials rubbing together. If you have a large frictional force it will not push the object backwards. For example, if I have a car traveling on a piece of sandpaper (I have no idea how or why) if the frictional force going against the car is greater than the car pushing forward, the sandpaper wont magically push the car backwards...
Correct me if I'm wrong, but a force is a force and if they're not balanced then there's a change in movement, right? Newton's 1st Law?

Having a frictional force that's twice the pushing force seems a bit ridiculous, I think OP may have missed some important details..
0
8 years ago
#10
(Original post by Ruthless Dutchman)
Correct me if I'm wrong, but a force is a force and if they're not balanced then there's a change in movement, right? Newton's 1st Law?

Having a frictional force that's twice the pushing force seems a bit ridiculous, I think OP may have missed some important details..
Quite. A force is very much a force, but a Frictional Force is not as simple as you are refering. A Frictional Force, in fundamentals is the repulsion of electrostatic forces upon one another. The OP said that there was a block on the table, and using my common sense I assumed that this frictional force was acting upon the block by the table. Since I know that the Frictional Force wouldn't cause any movement in such an environment I assumed that the Frictional Force would counter the Force of the Movement, as one would expect in such a scenario.
If the object had been moving, you are very correct, the object would have a change in it's movement, namely that it would slow down. Since however the object is stationary, it can not slow down any more, thus I must assume that the object is stationary. If the Frictional force were to have made the Object move the object would have to have miniscule mass, in order for the electrostatic forces to overcome the gravitational pull of the Earth and repel the object.
Since this was a real life example, that we can all very easily see, I simply used my knowledge of the experiment to say that, as Imnormal said that the force is a maximum frictional force. What both you and Imnormal have said are in theory perfectly correct, but they wouldn't work on such a experiment as you can very easily see if you test it out. However, I think if the OP gives a little bit more information we'll be able to see if it is a maximum frictional force as I have assumed or whether this is an incredibly theoretical situation.
0
#11
The diagram shows that to move the block you would need to exert twice as much power to overcome the friction.

Posted from TSR Mobile
0
8 years ago
#12
Exert twice as much power does not make sense.
You exert force not power.
Please post the complete original question and diagram.
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