Three forces applied to a trunk

[TS656577]

Homework Statement

The figure shows three forces applied to a trunk that moves leftward by 2.8 m over a frictionless floor. The force magnitudes are F1 = 5.5 N, F2 = 8.7 N, and F3 = 2.6 N, and the indicated angle is θ = 60°. (a) During the displacement, what is the net work done on the trunk by the three applied forces, the gravitational force, and the normal force? (b) Is there a net transfer of energy to or from the trunk? (c) Does the kinetic energy of the trunk increase or decrease?

Homework Equations

W=Fd

The Attempt at a Solution

I know that Force 1 did 15.4 J of work (5.5 times 2.8) and I know that Force 2 did -12.18J of work (dotted line = 4.35 and 4.35 times 2.8= 12.18) Force 3 didnt do any work on the block. I don't know how to tie it all together
D

 

[Hootenanny]

There isn't sufficient information, where is the angle 'theta' measured from for example? A diagram or further explanation would be helpful.

 

[TS656577]

oops...forgot to upload the diagram!

 

[Hootenanny]

Okay, all your answers thus far are correct. For question (a) the net work done is simply the sum of all the work done by the individual forces. With respect to the work done by gravity and the normal force, you have to decide if there was any displacement that wasn't perpendicular to the direction of the normal force and the weight.

The solution to (b) follows directly from (a), positive work is energy in, negative work is energy out.

I'm sure you can figure out (c) yourself

 

[TS656577]

The work due to normal force and gravitational force is 0. So is my answer 3.22

 

[Hootenanny]

The work due to normal force and gravitational force is 0. So is my answer 3.22

3.22 Joules. Correct .

 

[TS656577]

THANKS! and i got the last two!

 

[Hootenanny]

THANKS! and i got the last two!

A pleasure, I hardly did any work