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Block 1 with mass m1 sits on top of Block 2 with mass m2. While m1 is greater than m2, they have an identical length, L. Which of the following statements accurately describes the torques in this two-block system?
Setup Image: https://cdn.kastatic.org/ka-perseus-images/d3e1a8531246c68f9897dd7b37221f3ff305ebab.png
- Choice A The weight of Block 1 through its center of mass produces a clockwise torque about the right end of Block 2.
- Choice B - If Block 2 were shifted to the left along with Block 1 without toppling off, the weight of block 2 would create a clockwise torque that is offset by the weight of Block 1 which creates a counterclockwise torque.
- (Choice C - Correct) The normal force on Block 1 produces a clockwise torque and the weight of Block 1 is producing a counterclockwise torque with the fulcrum at the right end of Block 1.
- (Choice D) If Block 1 were shifted to the right the increasing clockwise torque on Block 1 is balanced by an increasing normal force on Block 1.
Hints:
- If the force acts downwards to the left or upwards to the right of the fulcrum, then there is a counterclockwise (CCW) torque. If the force acts downwards to the right or upwards to the left of the fulcrum, then there is a clockwise (CW) torque.
Forces will act from the center of mass if possible, and the fulcrums are the top right edge of Block 2 and the left edge of the desk.
- If Block 2 were shifted to the left, the center of mass moves to the left of the fulcrum, so the weight creates a CCW torque, not CW. The weight of Block 1 acts to the right of the same fulcrum downwards creating a CW torque, not CCW.
- If Block 1 were shifted to the right, as the center of mass moves to the right of the fulcrum, it will create a CW torque that topples off Block 1. However, the small normal force from Block 2 has been decreasing as Block 1 moved to the right.
- The weight of Block 1 acts to the left of the fulcrum downwards, and the weight will produce a CCW torque, not CW.
- There is a normal force from Block 2 on Block 1 that acts to the left of the fulcrum upwards, producing a CW torque.
Hint Diagram: https://cdn.kastatic.org/ka-perseus-images/94ca5ff24d6864f7fa8ca690a3698f772f8d3afd.png
My question: Do we have the direction of torque for weight in choice C going counterclockwise, due to it originating from block 1's center of mass (in the middle of the block), which would make the force to the left of the fulcrum, producing a counterclockwise torque? I'm also not gettting where we put the fulcrum for the other options.
Setup Image: https://cdn.kastatic.org/ka-perseus-images/d3e1a8531246c68f9897dd7b37221f3ff305ebab.png
- Choice A The weight of Block 1 through its center of mass produces a clockwise torque about the right end of Block 2.
- Choice B - If Block 2 were shifted to the left along with Block 1 without toppling off, the weight of block 2 would create a clockwise torque that is offset by the weight of Block 1 which creates a counterclockwise torque.
- (Choice C - Correct) The normal force on Block 1 produces a clockwise torque and the weight of Block 1 is producing a counterclockwise torque with the fulcrum at the right end of Block 1.
- (Choice D) If Block 1 were shifted to the right the increasing clockwise torque on Block 1 is balanced by an increasing normal force on Block 1.
Hints:
- If the force acts downwards to the left or upwards to the right of the fulcrum, then there is a counterclockwise (CCW) torque. If the force acts downwards to the right or upwards to the left of the fulcrum, then there is a clockwise (CW) torque.
Forces will act from the center of mass if possible, and the fulcrums are the top right edge of Block 2 and the left edge of the desk.
- If Block 2 were shifted to the left, the center of mass moves to the left of the fulcrum, so the weight creates a CCW torque, not CW. The weight of Block 1 acts to the right of the same fulcrum downwards creating a CW torque, not CCW.
- If Block 1 were shifted to the right, as the center of mass moves to the right of the fulcrum, it will create a CW torque that topples off Block 1. However, the small normal force from Block 2 has been decreasing as Block 1 moved to the right.
- The weight of Block 1 acts to the left of the fulcrum downwards, and the weight will produce a CCW torque, not CW.
- There is a normal force from Block 2 on Block 1 that acts to the left of the fulcrum upwards, producing a CW torque.
Hint Diagram: https://cdn.kastatic.org/ka-perseus-images/94ca5ff24d6864f7fa8ca690a3698f772f8d3afd.png
My question: Do we have the direction of torque for weight in choice C going counterclockwise, due to it originating from block 1's center of mass (in the middle of the block), which would make the force to the left of the fulcrum, producing a counterclockwise torque? I'm also not gettting where we put the fulcrum for the other options.
