Bird feeder's force

Feb 2011
7
0
A 1.1 kg bird feeder hangs from a horizontal tree branch. The bird feeder is attached to the branch at a point that is 1.1 m from the trunk. What is the amount of torque exerted by the bird feeder on the branch? The origin is at the pivot point, where the branch attaches to the trunk.

Given: 1.1 kg mass
1.1 m from trunk, which is the origin of the system.

Objective: Find the amount of torque exerted by the bird feeder on the branch.

Battle Plan:
Find the force exerted by the bird feeder from the mass.
Multiply the distance from the trunk by the mass of the bird feeder

Outcome:
Force = mass x acceleration
Force = 1.1 kg x 0m/s^2
Force = 0 N
0 N x 1.1 m = 0 N*m


My real question is, how do I get newtons from the mass of that birdfeeder? The feeder isn't accelerating anywhere, so the force has to be zero, right?

But they tell me the answer to this problem is 2.83e4 N*m.

I'd appreciate your help.
-Tom
 

topsquark

Forum Staff
Apr 2008
3,009
635
On the dance floor, baby!
A 1.1 kg bird feeder hangs from a horizontal tree branch. The bird feeder is attached to the branch at a point that is 1.1 m from the trunk. What is the amount of torque exerted by the bird feeder on the branch? The origin is at the pivot point, where the branch attaches to the trunk.

Given: 1.1 kg mass
1.1 m from trunk, which is the origin of the system.

Objective: Find the amount of torque exerted by the bird feeder on the branch.

Battle Plan:
Find the force exerted by the bird feeder from the mass.
Multiply the distance from the trunk by the mass of the bird feeder

Outcome:
Force = mass x acceleration
Force = 1.1 kg x 0m/s^2
Force = 0 N
0 N x 1.1 m = 0 N*m


My real question is, how do I get newtons from the mass of that birdfeeder? The feeder isn't accelerating anywhere, so the force has to be zero, right?

But they tell me the answer to this problem is 2.83e4 N*m.

I'd appreciate your help.
-Tom
The bird feeder has a weight, does it not?

-Dan
 
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Feb 2011
7
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The bird feeder has a weight, does it not?

-Dan
2.42508488 pounds. So how do you derive newtons from pounds?

1 pound is 4.448 N, so

= 10.78677755 N

10.78677755 N x distance: 1.1 m = 11.8654553 N*m
 

Unknown008

PHF Hall of Honor
Jun 2010
609
137
Mauritius
Okay, I'm not used to the British system, but the weight of the breeder is given my mg, which is 1.1 kg * 9.8 m/s^2. Hence why I don't use the pound to Newton conversion.

This gives you a final answer of 11.858 which you round up to 12 Nm (your question gives the values to 2 sf, you give the answer to 2 sf)

Rounding your answer gives the same thing, so that would be good too :)
 
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Feb 2011
7
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Thank, but the key says the answer is 2.84e4 Nm. Any suggestions?