Simple machines make work easier, but they do not decrease the amount of work you have to do. For a wheel and axle, the input distance is the circumference of the wheel, and the output distance is the circumference of the axle. Work power and machines worksheet. 1 m. What is the efficiency of the machine? Show them that it looks more like a lever if the wheel is replaced by a crank. 8(a), the worker uses a type of lever to exert a small force over a large distance, while the pry bar pulls up on the nail with a large force over a small distance. Be sure students do not equate machines and motors by asking for (and, if necessary, providing) examples of machines that are not motorized.
This results in a smaller force acting over a greater distance at the end of the resistance arm. So, why is a simple machine useful? Work and machines worksheet pdf answers. Most students should skip to the final two or three minutes which explain the basics of calculating IMA of a lever from different ratios. It shows a derivation using trig functions that is beyond the scope of this chapter. Our worksheets on the simple machines are ideal for grade 3, grade 4, and grade 5. A wedge is simply two inclined planes back to back. After they have discovered the three kinds, with or without your help, ask if they can think of examples of the types not shown in Figure 9.
Reduce the radius of the pulley. All sloping, paved surfaces for walking or driving are inclined planes. In real life, some of the applied work always ends up as wasted heat due to friction between moving parts. The heavier child sits farther from the fulcrum. Because the amount of work is not changed, the term f d does not change, but force can decrease if distance increases. Work and machines worksheet pdf answer. Have the students compare this screw to a wood screw and a circular stairway. Don't let them confuse the term with complicated machines such as computers. Increase the number of ropes supporting the load. Recall that in closed systems the total amount of energy is conserved. In this section you will apply what you have learned about work to find the mechanical advantage and efficiency of simple machines. If the rod has a diameter of 1 cm and the IMA of the machine is 6, what is the radius of the handle? State the equation for efficiency of a simple machine, and calculate Wo and Wi.
An answer key is included for each worksheet. Beautifully baked into our free, printable simple machines worksheets is the fact that in life we are increasingly at the mercy of machines, simple or complex, and therefore we must equip ourselves to identify each machine that we encounter every day as a lever, pulley, inclined plane, wedge, wheel and axle, or screw. Since both have different weights, they will never be in balance. Force applied to the outside of the wheel causes a greater force to be applied to the rope that is wrapped around the axle. This way bales of hay could be lifted into the hay loft without getting wet. A machine cannot increase the amount of energy you put into it. Give some examples: hand-powered windlass, steering wheel, door knob, and so on. This printable simple machines worksheet, where the task is for the grade 3 children to match each simple machine to an example by drawing a line, will get the quiet machine enthusiasts splendidly eloquent. The car, with its engine and four wheels has to be a complex machine. Check Your Understanding. Instruct the child to cut each simple-machine picture and glue it beside the description that best matches. In the formula for IMA, the distance between screw threads is called pitch and has the symbol P. [BL] [OL] Suggest that a screw is classified as a separate type of simple machine perhaps because it looks so different from what it really is—an inclined plane which sometimes is turned by a lever.
Examples of this type of lever are baseball bats, hammers, and golf clubs. Note that, when using an inclined plane the load moves, but when using a wedge the load is stationary and the machine moves. When you go down a slide at a park, the simple machine whose industry you owe a debt of gratitude to is an inclined plane. 11 is actually a lever attached to a circular inclined plane. Wo and Wi can always be calculated as a force multiplied by a distance, although these quantities are not always as obvious as they are in the case of a lever. The reason why this cut and glue pdf for grade 4 and grade 5 is a sure scene-stealer is it defines each simple machine as simply as could be. While we push staples through pieces of paper in order to fasten them together nearly every day, little do we realize we are making a simple machine, a lever to be specific, work hard. A complex machine is a combination of two or more simple machines. The last part shows how to calculate the IMA of an inclined plane. Calculating Mechanical Advantage and Efficiency of Simple Machines. Although it cannot change the amount of work you do, a simple machine can change the amount of force you must apply to an object, and the distance over which you apply the force. Both children sit at equal distance from the fulcrum. Explain that the combined mechanical advantage can be great. Cars and other vehicles are combinations of many machines.
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