Then why did we do so? The difference between the predicted and the actual mass was unavoidable as the masses had impeded our view of the measurements on the meter stick. If necessary, slide the slip-knot one way or another until the balance point for the empty dowel is found. Similarly, your vehicle's engine applies torque to the axles so that your wheels will rotate. In other words, torque is a force that creates rotation. We compared the mass we obtained with the actual mass of the unknown mass and the mass clamp.
We solved for what the mass should be and then measured the mass to see how close to the actual we obtained. Record the sum of the mass of the hanger and a mass of your choice. Torque usually produces a rotation of a body. One example for this is a beam balancing at its center on a fulcrum with two weights at either end. In mathematical terms, torque is the product of a force and a perpendicular radius. As seen below our error value is less than 1% which related to human ability related faulties.
We will also make the determination of the centre of gravity of the meter stick, comparison of the experimentally determined location for a given applied force to produce rotational equilibrium with the location predicted theoretically and finally determination of the mass of an unknown object. In first trying the meter stick stroke the table in short time. Calculate the net torque on this system about the point support and compare with the expected value. The moment arm is defined as the perpendicular distance from the axis-of-rotation to the line-of- action of the force. When an object is in rotational equilibrium, we can use the fact that the sum of the torques must be zero to find the different individual forces acting on that object. This condition is indicated in the figure shown above.
The main difference is that with rotation we are looking at torques instead of forces. In the second example the weight on the palm of the hand is at a greater distance from the elbow. A torque is the product of a force and a moment arm. If the body is to be in equilibrium, it must be in equilibrium both with respect to translation and to rotation. Next measure the distance from the balance point to mass 2 and record as L2.
To make it clear, we draw the meter stick like this position because it is a common misconception that if a meterstick is in equilibrium then it will remain parallel to ground. A force applied as described in the above examples results in a torque on a body. We calculated unknown mass as 52,2 g. Again, we find that this must mean the object is either stationary or moving at a constant angular velocity. Finally you will use the principle of rotational equilibrium to determine the mass of an unknown object.
Record the masses and positions. We also know that the net torque is the sum of the individual torques. In the diagram a 1. We developed the idea that both force and lever arm produce torque. A torque is the product of a force and a moment arm. Using one of the paperclips place the unknown on the right side of the dowel at some location. For the meter stick to be in equilibrium, and for it to balance the masses it carries, the torque must be equal.
The center of gravity of the meter stick is 29 cm away. Slide the masses across the meter stick until they are balanced. In any case, our error % values are less than 5%. We will now use this same procedure to determine the unknown mass of an object. Measure the distances from mass one to the balance point and record as L1 and measure the distance from the unknown to the balance point and record as L2 in Table 3. Assume that the masses of the rubber bands are negligible. It is said to be in rotational equilibrium.
In rotational equilibrium, an object either will not be moving or moving at a constant angular velocity. Place about 200 grams at 90 cm on the meter stick and balance the system by changing the balance point of the meter stick. We adjusted the unknown mass to balance the meter stick. Using one of the paperclips place the unknown on the right side of the dowel at some location. All lever arm distances are measured from the knife edge, which serves as the point of support.
The negative signs make sense because they show that the force due to gravity and the frictional force are acting in opposite directions from the normal force and applied force respectively. Procedure The results of this experiment should be quite good, so be patient when balancing the beam. We did use calculations to see how close to 0 we got for a torque net but weren't able to compare to any tests. Instructions Before viewing an episode, download and print the note-taking guides, worksheets, and lab data sheets for that episode, keeping the printed sheets in order by page number. It is said to be in rotational equilibrium. Sum the torques about your pivot point O and compare with the expected value. We changed our third mass on the left side with a new unknown mass.
The pennies, plastic bag and one piece of string constitute mass 1. Alternatively, this can be stated that the sum of the clockwise torques must equal the sum of the counter-clockwise torques. Discussion of Rotational Equilibrium Principles When an object is in rotational equilibrium, it is either not rotating or rotating at a constant rate. We found the new center of gravity with a 200 g mass hanging at the 90 cm mark on the meter stick. Mass 2 is the bag with 60 pennies plus a string and plastic bag. That ended up being 31.