Tension pulls the bucket upward

[21ducks]

I have been trying to figure out how this works. I know what the answer is since someone else has previously posted the answer in the forums. I want to learn how to do it though. Here is the question:

A 3.0 kg bucket is being lowered by a rope into a 10 m deep well, starting from the top. The tension in the rope is 9.8 N. The acceleration of the bucket will be:

6.5 m/s/s downward.

He used the following formula Net F / m = a which is 19.66 / 3.0 kg = 6.5 m/s/s.

How did he get the 19.66??

 

[krnhseya]

draw a FBD of the bucket.
tension pulls the bucket upward and w=mg pulls it downward.
if you sum the force in either direction, you should get that.

i've used 9.81 as the gravity and i got 19.63 as force instead of 19.66 but it should be fine.

 

[mgb_phys]

From the weight of the bucket (3.0kg * 9.81m/s/s) less the tension (9.8N) = 19.66

 

[21ducks]

Thanks! So let me see if I understand now. Do I multiply 3.0 X 9.81 = 29.43 for weight and then subtract the tension to get 29.43 - 9.8 = 19.63. Then plug the 19.63 into the Net F/ m = a ?

 

[21ducks]

Perfect! Thank you!