Calculating Energy Lost due to Friction

In summary, the conversation is about finding the work done by a 68.9 N force acting at an angle on a 15.6 kg block that is dragged over a rough surface. The work done is calculated to be 297.74 J. The question of how much energy is lost due to friction is also discussed, with the correct calculation taking into account the reduced normal force caused by the pulling force.
  • #1
shrutij
25
0

Homework Statement


A 15.6 kg block is dragged over a rough, horizontal surface by a 68.9 N force acting at 19.7 degrees above the horizontal. The block is displaced 4.59 m, and the coefficient of kinetic friction is 0.286. Find the work done by the 68.9 N force.

How much energy is lost due to friction?


Homework Equations


W=F (Δr) cos∅
Friction (kinetic)= μk* m*g


The Attempt at a Solution


I found the work done by the 68.9 N force using the equation above to get 297.74 J.
The energy lost due to friction should be simply the Force of kinetic friction multiplied by the displacement, right?
I did 0.286*15.6 kg* 9.81 to get 43.77 N as the force of kinetic friction.
Energy lost= Force friction * displacement i.e. 43.77 N * 4.59 m = 200.90 J, which is wrong.

What am I missing?
 
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  • #2
The normal force is reduced by the "lift" of the vertical component of the 68.9 N pulling force.
 
  • #3
So, normal force should be mg-68.9sin19.7 ?
 
  • #4
Yes, right on.
 
  • #5
Got it. Thanks so much!
 
  • #6
Most welcome! Good luck on the next one.
 

Related to Calculating Energy Lost due to Friction

1. What is friction?

Friction is a force that occurs when two surfaces are in contact and sliding against each other. It acts in the opposite direction of the motion and can cause objects to slow down or come to a stop.

2. How does friction cause energy to be lost?

When two surfaces are in contact and sliding against each other, friction causes the molecules of each surface to interact and create heat. This heat energy is a form of energy that is lost and cannot be used for work or other useful purposes.

3. Does the type of surface affect the amount of energy lost due to friction?

Yes, the type of surface does affect the amount of energy lost due to friction. Rougher surfaces create more friction and therefore more energy is lost. Smoother surfaces create less friction and therefore less energy is lost.

4. How can we reduce the amount of energy lost due to friction?

There are several ways to reduce the amount of energy lost due to friction. One way is to use lubricants or oils between two surfaces to create a smoother surface and reduce friction. Another way is to use rolling instead of sliding, as rolling friction is typically less than sliding friction. Additionally, using materials with less roughness or using materials that are designed to reduce friction, such as Teflon, can also help reduce energy loss due to friction.

5. Is it possible to eliminate energy loss due to friction entirely?

No, it is not possible to eliminate energy loss due to friction entirely. Friction is a natural phenomenon that occurs whenever two surfaces are in contact and moving against each other. However, we can minimize the amount of energy lost by using techniques such as those mentioned in the previous question.

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