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The force applied to the outer surface of each wheel must also beequal otherwise one of them would be accelerating more rapidly than the other, and again the teeth of the otherwheel would break. However, the forces the forces applied tothe axles are not equal. Returning to the concept of levers, we know that the distance from the fulcrum at which theforce is applied effects the force applied at another point, and a wheel and axle works like a lever. Equal forces are being applied toeach wheel, but on the larger wheel that force is being applied at a greater distance from the axle. Thus, for the larger wheel,the force on the axle is greater than the force on the axle of the smaller wheel.

Cams and cranks

Both cams and cranks are useful when a repetitive motion is desired. Cams make rotary motion a little more interesting by essentially moving theaxle off-center. Cams are often used in conjunction with a rod. One end of the rod is held flush against the cam by aspring. As the cam rotates the rod remains stationary until the "bump" of the cam pushes the rod away from the cam'saxle. Cams can be used to create either a linear repetitive motion such as the oneillustrated in , or a repetitive rotational motion such as using a cam and a rubber band .

Cams and Cranks

Cranks convert rotary motion into a piston-like linear motion. The best examples of cranks inaction are the drive mechanism for a steam locomotive and the automobile engine crankshaft. In a crank, the wheel rotatesabout a centered axle, while an arm is attached to the wheel with an off-centered peg. This arm is attached to a rod fixedin a linear path. A crank will cause the rod to move back and forth. If instead the rod is pushed back and forth, it will causethe crank to turn. On the other hand, cams can move their rods, but rods cannot move the cams.

Pulleys

Pulleys

Pulleys can be used to simply change the direction of an applied force or to provide aforce/distance tradeoff in addition to a directional change, as shown in . Pulleys are very flexible because they use ropes or chain to transfer force rather than a rigidobject such as a rod. Ropes can be routed through virtually any path. They are able to abruptly changedirections in three-dimensions without consequence, except, of course, additional friction. Ropes canbe wrapped around a motor's shaft and either wound up or let out as the motor turns.

How Compound Pulleys Work

illustrates how a compound pulley 'trades' force for distance through anaction/reaction force pair. In a double pulley, as the rope passes over the pulley the force is transmitted entirely butthe direction has changed. The effort is now pulling up on the left side of the bottom pulley. Now, for a moment forget thatthe end of the rope is tied to the bottom of the top pulley. The mechanics are the same if the rope is fixed to theceiling. The important thing is that the end of the rope is immobile. The effort is once again transmitted entirely as therope passes over the bottom pulley and there is a direction change. The end of the rope is attached to the ceiling so therope is pulling down on the ceiling with the force of the effort (and half of the force of the load). We assume that theceiling holds up, so this must mean that there is a force balancing out this downward force. The ceiling pulls up on therope as a reaction force. This upward force is equal to the effort and now there is an upward force on the right side ofthe bottom pulley. From the perspective of a free-body diagram the compound pulley system could be replaced by tying tworopes to the load and pulling up on each with a force equal to the effort.

The disadvantages of pulleys, in contrast to machines that use rigid objects to transfer force, areslipping and stretching. A rope will permanently stretch under tension, which may affect the future performance of adevice. If a line becomes slack, then the operation of a machine may change entirely. Also, ropes will slip and stickalong pulley wheels just like belts. One solution to the problems associated with rope is to use chain. Chain ispliable like rope, and is able to transfer force through many direction changes, but the chain links are inflexible intension, so that the chain will not stretch. Chains may also be made to fit on gears so that slipping is avoided.

Questions & Answers

A golfer on a fairway is 70 m away from the green, which sits below the level of the fairway by 20 m. If the golfer hits the ball at an angle of 40° with an initial speed of 20 m/s, how close to the green does she come?
Aislinn Reply
cm
tijani
what is titration
John Reply
what is physics
Siyaka Reply
A mouse of mass 200 g falls 100 m down a vertical mine shaft and lands at the bottom with a speed of 8.0 m/s. During its fall, how much work is done on the mouse by air resistance
Jude Reply
Can you compute that for me. Ty
Jude
what is the dimension formula of energy?
David Reply
what is viscosity?
David
what is inorganic
emma Reply
what is chemistry
Youesf Reply
what is inorganic
emma
Chemistry is a branch of science that deals with the study of matter,it composition,it structure and the changes it undergoes
Adjei
please, I'm a physics student and I need help in physics
Adjanou
chemistry could also be understood like the sexual attraction/repulsion of the male and female elements. the reaction varies depending on the energy differences of each given gender. + masculine -female.
Pedro
A ball is thrown straight up.it passes a 2.0m high window 7.50 m off the ground on it path up and takes 1.30 s to go past the window.what was the ball initial velocity
Krampah Reply
2. A sled plus passenger with total mass 50 kg is pulled 20 m across the snow (0.20) at constant velocity by a force directed 25° above the horizontal. Calculate (a) the work of the applied force, (b) the work of friction, and (c) the total work.
Sahid Reply
you have been hired as an espert witness in a court case involving an automobile accident. the accident involved car A of mass 1500kg which crashed into stationary car B of mass 1100kg. the driver of car A applied his brakes 15 m before he skidded and crashed into car B. after the collision, car A s
Samuel Reply
can someone explain to me, an ignorant high school student, why the trend of the graph doesn't follow the fact that the higher frequency a sound wave is, the more power it is, hence, making me think the phons output would follow this general trend?
Joseph Reply
Nevermind i just realied that the graph is the phons output for a person with normal hearing and not just the phons output of the sound waves power, I should read the entire thing next time
Joseph
Follow up question, does anyone know where I can find a graph that accuretly depicts the actual relative "power" output of sound over its frequency instead of just humans hearing
Joseph
"Generation of electrical energy from sound energy | IEEE Conference Publication | IEEE Xplore" ***ieeexplore.ieee.org/document/7150687?reload=true
Ryan
what's motion
Maurice Reply
what are the types of wave
Maurice
answer
Magreth
progressive wave
Magreth
hello friend how are you
Muhammad Reply
fine, how about you?
Mohammed
hi
Mujahid
A string is 3.00 m long with a mass of 5.00 g. The string is held taut with a tension of 500.00 N applied to the string. A pulse is sent down the string. How long does it take the pulse to travel the 3.00 m of the string?
yasuo Reply
Who can show me the full solution in this problem?
Reofrir Reply
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Source:  OpenStax, Notes on basic mechanics for rice elec 201. OpenStax CNX. Jun 12, 2006 Download for free at http://cnx.org/content/col10357/1.1
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