Physics Force/tension problem

[ATL2123]

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Four 100-kg people are holding a 1200-kg inflated balloon by means of 4 ropes. Three people let go and the balloon accelerates upward at 2 m/s2. What is the tension in the rope that the last person is holding?


A.200 N
B.400 N
C.800 N
D.1200 N

Help!? I tried to balance the forces going up and down but that got me nowhere, and I thought it was C because the net acceleration would be (10-2) and multiply that by the mass of the person, but the answer is D

 

[FutureDoc2]

Four 100-kg people are holding a 1200-kg inflated balloon by means of 4 ropes. Three people let go and the balloon accelerates upward at 2 m/s2. What is the tension in the rope that the last person is holding?


A.200 N
B.400 N
C.800 N
D.1200 N

Help!? I tried to balance the forces going up and down but that got me nowhere, and I thought it was C because the net acceleration would be (10-2) and multiply that by the mass of the person, but the answer is D

Okay, this is a great conceptual question that TBR Physics will help you understand and answer in a matter of seconds! To answer this without using hard math is to find the force going down after the 3 people let go. If the remaining individual has a mass of 100kg, multiply this by 10 (gravity) to get the Weight= 1000N. So we know the W=1000N. The fact the question states the ballon accelerates upward at 2m/s^2, means that the upward force has to be greater than the force going down which is 1000N. With that said, the answer has to be anything above 1000N which leaves D. Doing it this way eliminates the time needed to work this problem out on paper and only requires 30 sec to do. Are you using TBR for Physics? TBR really gives good tactics for answering these type of questions. Let me know if this makes sense!

 

[ATL2123]

That totally makes sense, thanks! I've been using TBR only for the past week and I only went through Physics 2 stuff since my MCAT is so soon, but it's been a lot more helpful than TPR ever was!