- #1

rosedog09

- 14

- 3

- Homework Statement
- (Questions 7 and 8) Determine the magnitude and net torque acting on the object shown above. (See attached screenshot with figures)

- Relevant Equations
- T = F*r*sin(angle)

F = force

R= radius

Angle = angle of force

My AP Physics notes state that counterclockwise is generally positive and clockwise is generally negative. This makes sense to me and means forces on opposite sides of the pivot point which act in opposite directions will work together, and this is the logic I applied to answer the problems.

Instead of following this rule, my teacher is saying I should use the direction of the force (i.e two forces acting on opposite sides and in opposite directions of the pivot point will work against each other), but this does not make sense to me as applying and upward force to one side and a downward force to the other will result in a larger net rotation. Could someone explain this to me? Thanks in advance.

P.S Dont take online AP Physics :(

My Work

7.

Net Torque = -100(1) + 50(.5) - 50(.75) = -112.5 Nm

8. Net Torque = -100(.75)(sin30) - 150(.5)(sin30) = -75 Nm

Teacher Comments

I understand I should probably just trust my teacher, but the online program I am enrolled in has had multiple faulty answer keys and teacher misunderstandings to date, and I would like a more thorough explanation of my error.

Instead of following this rule, my teacher is saying I should use the direction of the force (i.e two forces acting on opposite sides and in opposite directions of the pivot point will work against each other), but this does not make sense to me as applying and upward force to one side and a downward force to the other will result in a larger net rotation. Could someone explain this to me? Thanks in advance.

P.S Dont take online AP Physics :(

My Work

7.

Net Torque = -100(1) + 50(.5) - 50(.75) = -112.5 Nm

8. Net Torque = -100(.75)(sin30) - 150(.5)(sin30) = -75 Nm

Teacher Comments

I understand I should probably just trust my teacher, but the online program I am enrolled in has had multiple faulty answer keys and teacher misunderstandings to date, and I would like a more thorough explanation of my error.