PDA

View Full Version : Tension


pttest
Jul20-09, 07:38 PM
1. The problem statement, all variables and given/known data
Buckets and a Pulley Two buckets of sand hang from opposite ends of a rope that passes over an ideal pulley. One bucket is full and weighs 130 N; the other bucket is only partly filled and weighs 65 N.
a) Initially, you hold onto the lighter bucket to keep it from moving. What is the tension in the rope?
b) You release the lighter bucket and the heavier one descends. What is the tension in the rope now?
c) Eventually the heavier bucket lands and the two buckets come to rest. What is the tension in the rope now?


2. Relevant equations



3. The attempt at a solution
a) Initially, you hold onto the lighter bucket to keep it from moving. What is the tension in the rope?
Tension is equal of the weight of the first bucket
T= 130N

b) You release the lighter bucket and the heavier one descends. What is the tension in the rope now?
Tension is equal of the weight difference between the of the first and secong buckets.
T= 130 - 65= 65N (But this answer is wrong. Could someone please explain?)

c) Eventually the heavier bucket lands and the two buckets come to rest. What is the tension in the rope now?
Tension is equal of the weight of the second bucket
T= 65N

djeitnstine
Jul20-09, 07:46 PM
for b) have you drawn a free body diagram of the buckets in flight?

pttest
Jul20-09, 08:49 PM
Yes, I did draw a free body diagram. In second situation since the heavier one descends (due to force of gravity) and the lighter one moves upwards I subtracted 65N from 130N.

Am I in right track? If not could you please explain...?

Thanks in advance

queenofbabes
Jul20-09, 09:22 PM
Unfortunately this question isn't that simple. Having drawn your free body diagrams, use Newton's 2nd Law on each bucket. What can you say about the acceleration of each bucket? Can you then solve for the tension?