Finding the net work done on an object

In summary, using the given information, a 325 N force acting at an angle of 27° on an object with a mass of 42.5 kg and a displacement of 320m results in a net work of 64825 J. The correct answer is given as 7.46*10^4 J.
  • #1
Shyamalan
2
0

Homework Statement


A 325 N force acts on an object with a mass of 42.5 kg at an angle of 27° , pulling the object along a flat surface. The coefficient of friction is 0.21 and the object's displacement is 320m.
Calculate the net work done on the object.

Homework Equations


W=Fdcos(θ) Fg=mg Ffr=μFN


The Attempt at a Solution


Ok, so I know FN in this case is equal to Fg, and the work done by the two is 0 J, because they perpendicular to the displacement. The work done by the pulling force is 325*320*cos(27) which is 92665 J. The friction force is 0.21*42.5*9.8 which is 87 N. The work done by the friction force is 87*320*cos(180) which is -27840 J. The net work is the sum of these two values, 92665+(-27840) which is 64825 J.

Now, the answer given is 7.46*10^4 J, which is one digit off of my answer. Am I doing something wrong or is there a typo in the answer I was given?
 
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  • #2
Welcome to PF!

Hi Shyamalan! Welcome to PF! :smile:
Shyamalan said:
Ok, so I know FN in this case is equal to Fg …

Noooo :rolleyes:
 
  • #3
Pfffft... Whoopsy, I got it now. XP
 

1. What is net work done on an object?

The net work done on an object is the sum of all the forces acting on the object multiplied by the distance the object moves. It is a measure of the overall change in the energy of the object.

2. How is net work done on an object calculated?

To calculate the net work done on an object, you must first determine all the forces acting on the object. Then, multiply each force by the distance the object moves in the direction of that force. Finally, add all of these values together to get the net work done.

3. What is the unit of measurement for net work done on an object?

The unit of measurement for net work done on an object is joules (J). This is the same unit used to measure energy.

4. Can the net work done on an object be negative?

Yes, the net work done on an object can be negative. This occurs when the forces acting on the object are in opposite directions, meaning that the object is moving in a direction opposite to the direction of the net force. In this case, the work done by one force is negative and the work done by the other force is positive, resulting in a net negative work.

5. How does the net work done on an object affect its energy?

The net work done on an object is directly related to its change in energy. If the net work done is positive, the object's energy will increase. If the net work done is negative, the object's energy will decrease. If the net work done is zero, there is no change in the object's energy.

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