![]() Further, the sum of all torques of all forces about any point must equal zero, for equilibrium. The board's weight resultant acts at its cg. The partners weight resultant acts at his cg. The moment (or torque) of a force about any point is equal to tjhe product of that force times the perpendicular distance from the line of action of that force to the point. I'm having trouble understanding what to use as the distance when determining torque.ġ)Since the partner is resting on a board supported by two points, why is the torque provided by the partner equal to his weight * distance from center of gravity and not the total distance from the end opposite of the scale?Ģ) Similarly, why is the force from the scale multiplied by the height of the lab partner and not the distance from the lab partner's center of gravity? Where d= distance from center of gravity. If the board's weight is 49N and the scale reading F is 350N, find the distance of your lab partner center of gravity from the left end of the board. You can now determine the position of his center of gravity by having him stretch out on a uniform board supported at one end by a scale. Use the equilibrium condition to determine the meter stick mass and check your result by massing the stick on the pan balance.Suppose your lab partner has a height L of 173 cm and a weight w of 715N. Restore balance by hanging a known mass from one side of the meter stick. Move the meter stick in its support so that the new pivot point is 10 cm away from its balance point. Then mass the unknown on the pan balance and compare your results. Use one of your known masses to produce rotational equilibrium and compute the unknown mass. After removing the other masses, suspend the supplied unknown mass from a convenient point on one side of the meter stick. How much does the net torque differ from the theoretical value of zero?ĭata: Pivot point on meter stick _ġ. ![]() Compare the clockwise and counterclockwise torques. But the mass times the lever arm differs only by the constant g, the acceleration of gravity, so for the balance condition it serves the same purpose.)Ĥ. (The torque, strictly speaking, is the weight times the lever arm. Compute the mass times the lever arm for each mass. Determine the lever arm associated with each mass and record the values in the data table below. Record the mass values and their positions.ģ. Suspend three masses from the meter stick as indicated in the sketch and move them until you balance the meter stick. Record the point on the stick at with it balances.Ģ. Balance the meter stick in a horizontal position on its knife-edge supports with no weights attached. Why is it not a good idea to use your dishwasher door as a step to get something out of the cabinet above it?ġ. Why is it hard to lift a long board by its end? If the invisible partner is the total mass of the board, where is this invisible partner sitting? This poor child has no one to play with, and had to design a "solitary see-saw". If you were caught without a mass balance, how could you get a number for the mass of the rock? Sum of clockwise torques = Sum of counterclockwise torques Write down your thoughts on these questions before beginning the experiment. When more than one torque acts to produce rotation about an axis it is often convenient to divide them into clockwise and counterclockwise torques, and the condition for rotational equilibrium is then This is illustrated in the diagram below for a bicycle pedal at different points in the pedaling motion the force of the rider's foot is more effective in producing rotation because the lever arm is longer. Where the lever arm is the perpendicular distance from the axis of rotation to the line of action of the force. Torque is a measure of a force's tendency to produce rotation and can be defined by ![]() This experiment will deal with rotational equilibrium and torques. The two conditions for an object to be in equilibrium are (1) zero net force and (2) zero net torque on the object. Torque and Equilibrium Torque and Equilibrium
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