Homework Help: Calculating Tension

1. Nov 15, 2009

physics_newb

1. The problem statement, all variables and given/known data
If the balloon in the diagram drawn below is accelerating upwards at 0.40 m/s2, calculate the tension in each piece of rope. Assume that the rope has no mass.
http://img261.imageshack.us/img261/964/capture2gm.png [Broken]
http://img261.imageshack.us/img261/964/capture2gm.png [Broken]

2. Relevant equations
a=0.4m/s^2
m1=6kg
m2=9kg

3. The attempt at a solution
Not sure how to calculate tension or what tension is

3. The attempt at a solution

Last edited by a moderator: May 4, 2017
2. Nov 15, 2009

physics_newb

anyone out there who can help me?

3. Nov 15, 2009

srmeier

You haven't put much effort into this (so it seems).

Hint: each block accelerates equally.

Last edited: Nov 16, 2009
4. Nov 15, 2009

physics_newb

actually i've been trying this for almost 45 minutes now and the thing is i don't know what tension is...is tension Fg? where Fg=m*a and it would me 15*.4?

5. Nov 15, 2009

holezch

tension is the force of the rope at some point

6. Nov 15, 2009

mg0stisha

Fg is not equal to m*a, Fg=mg, where g is the acceleration due to gravity, or 9.8m/s^2.
Fnet=ma

Also, tension is not Fg, it's a separate force.

7. Nov 16, 2009

physics_newb

Ok guys this is how far I got from what I understood....can somone tell me if this is right and how to get to the next step please? Thanks in advance...this sites been a real life saver!!!

Rope 1
a=0.40m/s^2
m=15kg
g=9.8m/s^2
F_t=?
F_g=?
Step1
F_g=mg
F_g=15*9.8
F_g=147m/s^2
Step2
F_t=

8. Nov 16, 2009

physics_newb

Hope no one fell asleep!! its 130am here hoping to solve this quickly...anyone still up or do i wake up early and check?

9. Nov 16, 2009

physics_newb

no one knows how to do this one? I've even woke up now :(

10. Nov 16, 2009

logickills

It is fairly hard to assist someone who doesn't understand the question they are asking. You need to figure out what tension is and how it is measured. You have to also see the relationships at hand between tension,gravity, and the effect the balloon has on the system.

A good starting place is to start with free body diagrams for each body in the system. Next sum your forces (only forces in the Y).

Last edited: Nov 16, 2009
11. Nov 16, 2009

physics_newb

So the above is wrong? LOL I know I do not udnerstand the question which is why I'm asking it! I would draw a FBD but not sure which way tension would be going...Fg would be down....and then Fapp would be up, where does Ft come in all this? I've also googled this and it seems that
ma=m(g+a)
but I'm not sure that is the formula we use as we have never been given that one as of yet

12. Nov 16, 2009

physics_newb

m=94.0kg
a=9.8m/s^2
CD=54kg/m
v=?
F_fric=?
Step 1
F_fric=ma
F_fric=94.0*9.8
F_fric=921.2m/s
Step 2:
921.2=54*v^2
921.2/54=v^2
17.1=v^2
√17.1=v
4.1=v
v=4.1m/s

13. Nov 16, 2009

holezch

sorry for not responding in time, I haven't been around the computer
tension is indeed ma=m(g+a). think about this.. you have a block that is being pulled down by the force of gravity.. yet it is going up? how is this so? it's because there is another force causing it to go up, and this force is apparently stronger than the force of gravity pulling the block down, since the whole system is going up. so how much greater is this force? well, we know that at the end of the day, the blocks are accelerating at 0.40 m/s2. so ma=m(g+a) (both forces act together to produce the net force, your other force would be the tension)

14. Nov 16, 2009

physics_newb

thanks holezch, but luckily for me I was able to find a formula on my own in time and the teacher told me that it was right...although i did it this way and am getting the same answer...thanks!

15. Jan 31, 2010

scienceroks

how do i calculate tension on a catapult

16. Feb 5, 2010

Tyler171

I just have a quick question if anyone can help...
I don't know how to calculate tension when I'm only given the tension of another thing and it's length... for example 2 ropes pulling on a ring, I'm given the tension and length of the 2 ropes and I am to find the third ropes tension pulling in the opposite direction... the only angles given are 90 degree angles.. please if anyone cane help.

17. Feb 6, 2010

srmeier

The purpose of the third rope is to most likely stop the ring from accelerating correct?