# Four 100 kg people are holding a 1200 kg inflated balloon

1. Feb 17, 2013

### blueberryfive

four 100 kg people are holding a 1200 kg inflated balloon by means of four ropes. three people let go and the balloon accelerates upward at 2 m/ s/s. what is the tension in the rope the last person is holding?

2. Feb 17, 2013

### ap123

What are your ideas on this?

3. Feb 17, 2013

### blueberryfive

t=mg?

4. Feb 17, 2013

### ap123

These are the 2 forces on the person, but if they were equal then the person would have an acceleration of zero.

Apply Newton's second law to the person.

5. Feb 17, 2013

### blueberryfive

ma=mg where a = 2 so m(a-g)=0 so 800 but I know it's actually a+g so 1200 why?

6. Feb 17, 2013

### ap123

ma = mg is not correct.

Newton 2 says that the total force on the person = ma
You've written the total force as just mg. You need to include the tension in here as well.

Just draw a quick diagram showing the forces on the person and the direction of the acceleration and then apply Newton 2, ( and be careful with the signs ).

7. Feb 17, 2013

### blueberryfive

oh! thank you very much