Conversion of percentage of effort to person months is straightforward. To calculate person months, multiply the percentage of your effort associated with the project times the number of months of your appointment. For example: 25% of a 9 month academic year appointment equals 2.25 (AY) person months (9 x 0.25= 2.25)
The AMA of a simple machine is the ratio of output to input forces. The IMA is the ratio of input distance to output distance.
To calculate the ideal mechanical advantage for an inclined plane, divide the length of the incline by the height of the incline. Example: An inclined plane that is 6 meters long and 3 meters high creates an ideal mechanical advantage of 2. The inclined plane increases the force that is being exerted by 2 times.
The input force (effort) is the amount of effort used to push down on a rod, or pull on a rope in order to move the weight. In this example, the force the little guy is using to pull the elephant is the input force.
The simple machines are the inclined plane, lever, wedge, wheel and axle, pulley, and screw.
The ideal mechanical advantage (IMA) - ignoring internal friction - of a lever depends on the ratio of the length of the lever arm where the force is applied divided by the length of the lever are that lifts the load. The IMA of a lever can be less than or greater than 1 depending on the class of the lever.
A lever is a simple machine that makes work easier for use; it involves moving a load around a pivot using a force. Many of our basic tools use levers, including scissors (2 class 1 levers), pliers (2 class 1 levers), hammer claws (a single class 2 lever), nut crackers (2 class 2 levers), and tongs (2 class 3 levers).
A doorknob is a wheel and axle type of simple machine. The knob represents the wheel while the central shaft or rod of the doorknob represents the
The screwdriver, in the most simple sense is actually a lever. The blade of the screwdriver is being used as a tiny lever to apply torque / rotary force… it may help to think about a flat bladed or “standard” screwdriver engaged in the slot on the head of the screw.
Mechanical advantage is defined as the resistance force moved divided by the effort force used. In the lever example above, for example, a person pushing with a force of 30 lb (13.5 kg) was able to move an object that weighed 180 lb (81 kg).
A wrench uses wheel and axle as simple machine to turn a bolt. The wrench and bolt act as wheel and axle.
The mechanical advantage of a machine is the ratio of the load (the resistance overcome by a machine) to the effort (the force applied). There is no unit for mechanical advantages since the unit for both input and output forces cancel out.
Classes of Levers, Simple and Compound Machines
| A | B |
|---|
| This simple machine is used to hold things together. It is made up of an inclined plane wrapped around a cylinder. | A screw. |
| A heavy object could be rolled up this simple machine, instead of lifting it straight up. | An inclined plane. |
Next we come to calculating the mechanical advantage of a lever. To do this, you divide the distance from the fulcrum, the point at which the lever pivots, to the applied force by the distance from the fulcrum to the resistance force. Using this picture, this means dividing distance b by distance a.
A lever is a simple machine which makes our work easier. Spanner is also called as Wrench. Spanner is a second class lever, where load is in between fulcrum and applied force. Small effort is used to move a large load.
As shown in the figure, the ideal mechanical advantage is calculated by dividing the radius of the wheel by the radius of the axle. Any crank-operated device is an example of a wheel and axle. Force applied to a wheel exerts a force on its axle.
Explanation: The Actual Mechanical Advantage AMA is equal to: The ideal mechanical advantage, IMA, is the same but in absence of FRICTION! In this case you can use the concept known as CONSERVATION of ENERGY.
Wheel and axle.
The ideal mechanical advantage (IMA) of a wheel and axle is the ratio of the radii. If the effort is applied to the large radius, the mechanical advantage is R/r which will be more than one; if the effort is applied to the small radius, the mechanical advantage is still R/r, but it will be less than 1.First- and second-class levers generally are very efficient, especially when the loads are located close to the fulcrum while efforts are further from the fulcrum (Figures A and C). The efficiency of first- and second-class levers will decrease when loads move further from the fulcrum (Figures B and D).
• Mechanical Advantage > 1 means that the output force will be greater than the input force. – (But the input distance will need to be greater than the output distance.)
Lever. These dominoes are a lever because levers are activated when something comes upon contact with another object, which means that the dominoes are a 3rd class lever.
