Solving Friction & Wood Homework

In summary: I fixed the equation for you.The applied force ##F_A## has to exceed the frictional force for the block to be accelerating forward (This is what I thought).Given that the net force in the horizontal direction is 0.58 [F] and the frictional force is 4.52N [B], the applied force must then be the sum of the frictional force and the net force because the applied force minus the frictional force is the net force.
  • #1
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Homework Statement



A block of wood which weighs 0.72 kg is being pushed across a floor. After 2s, the block has a velocity of 1.6m/s[F]. μK = 0.64.

a) Find the net force acting on the block of wood.
b) Find the force of friction acting of the block.
c) Find the force actually pushing the block of wood.

Homework Equations



##m = 0.72kg##
##Δt = 2s##
##μ_K = 0.64##
##\vec{v_H} = 1.6 m/s [F]##

The Attempt at a Solution



a) Okay so I want to find the net force acting on the wood. First off, the block has no movement in the vertical direction at all so we know ##F_N = F_G = ma = (0.72)(9.8) = 7.06N## and the final vertical force ##F_V = 0##.

If the block is increasing velocity over time horizontally, then it is accelerating horizontally. Using this acceleration we can find the force in the horizontal direction. I believe I can use this kinematic equation :

##\vec{v_H} = \vec{v_1} + \vec{a}Δt##
##1.6 m/s [F] = 0 + (2s) \vec{a}## [There is no initial horizontal velocity so ##\vec{v_1} = 0##]
##0.8 m/s^2 [F] = \vec{a}##

Now to find the net force which happens to be in the horizontal direction only, I use :

##\vec{F_H} = m \vec{a} = (0.72kg)(0.8 m/s^2 [F]) = 0.58N [F]##

Therefore the net force acting on the block of wood is 0.58N [F].

b) I think I need to use :

##F_K = μ_KF_N = (0.64)(7.06) = 4.52N##.

c) Logically the force acting on the wood should be the frictional force together with the net force

##F_A = F_K + F_H = 0.58N + 4.52N = 5.1N##

Therefore the block is being pushed with a force of 5.1N to get it to move forward.
 
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  • #2
you don't sseem to have a question? without doing the math it looks to be ok work. I am not sure about the very last equation. but like you say it seems logical to add the forces.
 
  • #3
Your answers look good to me.
 
  • #4
462chevelle said:
you don't sseem to have a question? without doing the math it looks to be ok work. I am not sure about the very last equation. but like you say it seems logical to add the forces.

The applied force ##F_A## has to exceed the frictional force for the block to be accelerating forward ( This is what I thought ).

Given that the net force in the horizontal direction is 0.58 [F] and the frictional force is 4.52N , the applied force must then be the sum of the frictional force and the net force because the applied force minus the frictional force is the net force.

EDIT : Thank you chev and barry for checking.
 
  • #5


Overall, you have correctly used the equations to find the net force, frictional force, and pushing force in this scenario. Your explanation is clear and well-organized. One thing to note is that in part b, you should specify that the frictional force is acting against the direction of motion, so it would be -4.52N. Otherwise, great job!
 

Related to Solving Friction & Wood Homework

1. How does friction affect wood?

Friction is a force that opposes motion between two surfaces. When two pieces of wood rub against each other, friction causes resistance, making it difficult to slide the pieces past each other.

2. How can I reduce friction between wood surfaces?

To reduce friction between wood surfaces, you can apply a lubricant such as wax or oil. Sanding or polishing the surfaces can also help to smooth out any roughness that may increase friction.

3. What is the coefficient of friction for wood?

The coefficient of friction for wood varies depending on the type of wood, its moisture content, and the type of surface it is in contact with. On average, the coefficient of friction for wood ranges from 0.2 to 0.6.

4. How does the weight of an object affect friction on a wooden surface?

The weight of an object has a direct impact on the amount of friction between it and a wooden surface. The heavier the object, the more force is applied to the surface, resulting in increased friction.

5. Can friction be completely eliminated between wood surfaces?

No, it is impossible to completely eliminate friction between wood surfaces. However, by using lubricants, sanding, or polishing, you can significantly reduce the amount of friction and make the surfaces easier to slide against each other.

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