Calculating Work: Lowering a Piano with Two Ropes

[sktgurl930]

Homework Statement

The two ropes are used to lower a 267.18 kg piano 5.34 m from a second-story window to the ground. How much work is done by gravity force? (T1=1864 N, θ1=64°, T2=1231 N, θ2=50°.)
How much work is done by T1 force?
How much work is done by T2 force?

Homework Equations

W=Fd
W=FdCos(angle)

The Attempt at a Solution

the first part worked out fine i had gotten
13982.004 J

but when I tired the second I got it wrong cause i did
W=FdCos(angle) and then subtracted it from the answer in the first part
and had gotten
-9618.56 J

and for the third part I just used
the equation
W=Fdcos(angle)

 

[Redbelly98]

but when I tired the second I got it wrong cause i did
W=FdCos(angle) and then subtracted it from the answer in the first part
and had gotten
-9618.56 J

Don't subtract the answer from the work done by gravity, just calculate W=FdCos(angle) for the answer.

and for the third part I just used
the equation
W=Fdcos(angle)

Yes, do it that way for both T1 and T2.

 

[sktgurl930]

I try but it doesn't work out
am i missing something?
is it positive or negative ?? i was thinking its negative goes its going down

 

[Redbelly98]

Yes, since the rope tension act against the direction of motion the work would be negative.

You need to use the angle between the rope and the direction of movement. You don't simply use 64 and 50 degrees, just because those are the numbers you see in the figure or problem statement.

 

[sktgurl930]

thank u
it makes sense now