Net Work Done: Solve Force Question Homework

• inflames829
In summary, the question asks for the net work done on an object under the influence of a force F=-4.3i+2.0j+1.5k Newtons and a displacement of d=-0.8i+1.8j+-3.6k metres, with a friction force of Ffr=-0.2. The work equation W=F.D is used to calculate the initial work, which is 1.64J. The friction force can also be used in the work equation, resulting in a work of -0.82J. However, the correct answer is 1.3J, indicating a mistake in the calculation.
inflames829

Homework Statement

A force F=-4.3i+2.0j+1.5k Newtons exerts a displacement of d=-0.8i+1.8j+-3.6k metres upon a small (ie mass is negligible) object. If the friction force is equal to Ffr=-0.2,, then what is the net work done upon the object?

The Attempt at a Solution

I know the net work is the sum of all the individual work and the work equation is W=F.D. So i tried to work out the work of the initial force stated by multiplying the force and displacement stated which i got 1.64J. I think the only other work is caused by the friction force but when i try to work that out (because the mass is negligable) i get 0. Can someone please help?

Mass is negligible only affects calculating the friction force using $\mu N$, but you already have the friction force. What can you do with it?

could i put it as the force in the work equation and put the distance as the displacement that's stated in the question?

Yes.

so i have 1.64 from the first force i worked out and if i put the friction force into the work equation w= -0.2 x D i get -0.82. If I add the two works i have i get 0.82, but the answer is 1.3... can you give me hints on what I've done wrong??

I get that also. From where did you get this problem?

1. What is net work done?

Net work done is the overall change in energy that occurs when a force is applied to an object and causes it to move a certain distance.

2. How do you calculate net work done?

To calculate net work done, you multiply the magnitude of the force applied to the object by the distance it moves in the direction of the force. This can be represented by the formula W = Fd, where W is net work done, F is the force, and d is the distance.

3. What units are used for net work done?

Net work done is typically measured in joules (J), which is the standard unit for energy. However, other units such as kilojoules (kJ) or foot-pounds (ft-lb) may also be used.

4. How does the direction of the force affect net work done?

The direction of the force applied to an object is important in determining net work done. If the force is applied in the same direction as the motion of the object, then the net work done will be positive. However, if the force is applied in the opposite direction of the object's motion, the net work done will be negative.

5. Can net work done ever be negative?

Yes, net work done can be negative if the force applied to an object is in the opposite direction of its motion. This indicates that the object is losing energy and moving in the opposite direction of the force applied.

• Introductory Physics Homework Help
Replies
8
Views
276
• Introductory Physics Homework Help
Replies
4
Views
1K
• Introductory Physics Homework Help
Replies
9
Views
1K
• Introductory Physics Homework Help
Replies
90
Views
3K
• Introductory Physics Homework Help
Replies
11
Views
1K
• Introductory Physics Homework Help
Replies
7
Views
1K
• Introductory Physics Homework Help
Replies
56
Views
2K
• Introductory Physics Homework Help
Replies
12
Views
829
• Introductory Physics Homework Help
Replies
29
Views
1K
• Introductory Physics Homework Help
Replies
7
Views
3K