The efficiency represents the proportion of the energy expended that can be converted into usable force. For an electric motor , this means that only a portion of the supplied electrical power remains in the form of mechanical drive power. One option is to dispense with a transmission altogether.
Direct drives, e. The drives can generate extremely high torques without having to accept gear losses. This also offers advantages over hydraulic systems, since there are no pressure losses. When calculating drive torque, the gear loss factor can be ignored completely. The efficiency reaches a very high level here, which in turn allows greater approximation to ideal conditions. In practice, it is usually not necessary to calculate the drive torque.
Often, it is only important to actually be able to reach a high torque, e. These include:. We call this rotational counterpart torque. In everyday life, we rotate objects about an axis all the time, so intuitively we already know much about torque.
Consider, for example, how we rotate a door to open it. First, we know that a door opens slowly if we push too close to its hinges; it is more efficient to rotate a door open if we push far from the hinges. Second, we know that we should push perpendicular to the plane of the door; if we push parallel to the plane of the door, we are not able to rotate it. Third, the larger the force, the more effective it is in opening the door; the harder you push, the more rapidly the door opens.
The first point implies that the farther the force is applied from the axis of rotation, the greater the angular acceleration; the second implies that the effectiveness depends on the angle at which the force is applied; the third implies that the magnitude of the force must also be part of the equation. Note that for rotation in a plane, torque has two possible directions.
Torque is either clockwise or counterclockwise relative to the chosen pivot point. Figure shows counterclockwise rotations. Figure Torque has both magnitude and direction. Note that the greater the lever arm, the greater the magnitude of the torque. In terms of the lever arm, the magnitude of the torque is.
The torque in Figure is positive because the direction of the torque by the right-hand rule is out of the page along the positive z -axis. The disk rotates counterclockwise due to the torque, in the same direction as a positive angular acceleration.
Any number of torques can be calculated about a given axis. The individual torques add to produce a net torque about the axis. When the appropriate sign positive or negative is assigned to the magnitudes of individual torques about a specified axis, the net torque about the axis is the sum of the individual torques:. In the following examples, we calculate the torque both abstractly and as applied to a rigid body.
Four forces are shown in Figure at particular locations and orientations with respect to a given xy -coordinate system. Find the torque due to each force about the origin, then use your results to find the net torque about the origin. This problem requires calculating torque. All known quantities——forces with directions and lever arms——are given in the figure. The goal is to find each individual torque and the net torque by summing the individual torques.
Note that each force that acts in the counterclockwise direction has a positive torque, whereas each force that acts in the clockwise direction has a negative torque. You likely know that if you push or pull on an object exert force , it will move a distance. The distance it moves depends on how heavy the object is and how much force you apply. However, if the object is fixed at some point called the "rotational point" or "axis" , and you push or pull on the object at some distance from that point, the object will instead rotate around that axis.
The most basic way to calculate torque is to multiply the Newtons of force exerted by the meters of distance from the axis. There's also a rotational version of this formula for 3-dimensional objects that uses the moment of inertia and angular acceleration. Calculating torque is a physics concept requiring an understanding of algebra, geometry, and trigonometry. To calculate torque, start multiplying the mass of the object exerting force by the acceleration due to gravity, which is 9.
If more than one force is present, add up all the torques to get the net torque of the combined forces. For tips on how to calculate torque using angular acceleration, read on! Did this summary help you? Yes No. Log in Social login does not work in incognito and private browsers. Please log in with your username or email to continue. No account yet? Create an account. Edit this Article. We use cookies to make wikiHow great. By using our site, you agree to our cookie policy.
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Is it a length unit or a mass? Add a comment. Active Oldest Votes.
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