Torque and Rotational Motion
A square plate has forces applied at each of its four corners. Each side of the plate has a length . Force is applied at two of the corners, while force 2F
is applied at the other two corners. Determine the net torque about the center of the square.
0
2FL
4FL
A force of 10 N is applied at a distance of 2 m from the axis of rotation. The angle between the position vector and the force vector is 60 degrees. What is the magnitude of the torque?
10 Nm
17.3 Nm
20 Nm
5 Nm
A uniform beam of length and weight is supported by two supports, one at each end. A person of weight 2W
stands a distance from one end. What are the reaction forces at each support?
3W/4 and 5W/4
W and 2W
W/2 and 3W/2
W/4 and 7W/4
A force is applied to a wrench to tighten a bolt. Which of the following will result in the greatest torque?
Applying a large force at an angle of 45 degrees to the wrench.
Applying a small force perpendicular to the wrench far from the bolt.
Applying a large force perpendicular to the wrench close to the bolt.
Applying a small force at an angle of 30 degrees to the wrench close to the bolt.
A 20 N force is applied at an angle of 30 degrees to a door at a distance of 0.5 m from the hinges. What is the magnitude of the torque applied to the door?
5.0 Nm
10.0 Nm
8.66 Nm
2.5 Nm
In a force diagram for torque analysis, which forces should be excluded?
Forces that cause rotation.
Forces that pass directly through the axis of rotation.
Forces with large magnitudes.
Forces applied perpendicular to the lever arm.
If the position vector points in the positive x-direction and the force vector points in the positive y-direction, what is the direction of the torque vector ?
Positive x-direction
Positive y-direction
Positive z-direction
Negative z-direction

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A force vector is given by N, and the position vector is given by m. Calculate the torque vector .
2\hat{i} - 3\hat{j} - \hat{k}
4\hat{i} - 3\hat{j} + 5\hat{k}
4\hat{i} - \hat{j} - 5\hat{k}
2\hat{i} + 3\hat{j} + \hat{k}
A seesaw has two people sitting on it. Person A applies a torque of 30 Nm counter-clockwise, and Person B applies a torque of 20 Nm clockwise. What is the net torque on the seesaw, and is it in rotational equilibrium?
50 Nm counter-clockwise, not in equilibrium
10 Nm counter-clockwise, not in equilibrium
50 Nm clockwise, not in equilibrium
10 Nm clockwise, in equilibrium
A wrench of length 0.2 m is used to tighten a bolt. A force of 50 N is applied at an angle of 30 degrees to the wrench. What is the magnitude of the torque applied to the bolt?
5.0 Nm
8.66 Nm
10.0 Nm
2.5 Nm