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Mechanical Systems

Mechanical Systems. Review March 2010. True/False. When you use your thumb and index finger to pull up your socks, you are using a first-class lever. For a third-class lever, the load force always exceeds the effort force. Multiple Choice. When arm-wrestling, your arm is acting as

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Mechanical Systems

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  1. Mechanical Systems Review March 2010

  2. True/False • When you use your thumb and index finger to pull up your socks, you are using a first-class lever. • For a third-class lever, the load force always exceeds the effort force.

  3. Multiple Choice When arm-wrestling, your arm is acting as • A first-class lever • A second-class lever • A third-class lever • None of these because the arm cannot be a lever

  4. True/False • To make the toy top spin, you spin the axle, creating a speed advantage for the wheel. • Torque and ideal mechanical advantage are measured in newton-metres.

  5. Multiple Choice The exercise handgrip is • A first-class lever • A second-class lever • A third-class lever • Either a second-class lever or a third-class lever, depending on where the fulcrum is considered to be

  6. Multiple Choice The IMA of the handgrip is • 3 • 1/3 • 4 • 1/4

  7. True/False • If the effort distance for a machine part is greater than the load distance, then the machine provides a force advantage. • Scissors are an example of a second-class lever combined with an inclined plane.

  8. Multiple Choice For any machine, as the friction of the moving parts increases, • The AMA and the % eff decrease • The AMA and the % eff increase • The AMA increases but the % eff decreases • The AMA decreases but the % eff increases

  9. True/False • In the equation for torque, the force F is perpendicular to the rigid object. • To obtain a force advantage for a wheel and axle, the effort force must be applied to the wheel.

  10. Multiple Choice As the angle of a wheelchair ramp changes from 10° to 20°, • The effort force falls and the AMA rises • Both the effort force and the AMA rise • Both the effort force and the AMA fall • The effort force rises and the AMA falls

  11. True/False • To increase the force of a machine, the distance from the fulcrum must be decreased. • The torque on a rigid object is greater when the applied force is parallel to the rigid object.

  12. Multiple Choice When using a hammer to remove a nail from a board, • The hammer acts as a third-class lever with an AMA greater than one • The hammer acts a second-class lever with an AMA greater than one • The hammer acts as a first-class lever with an AMA greater than one • None of the above

  13. True/False • In any machine that experiences friction, the ideal mechanical advantage exceeds the actual mechanical advantage. • A machine with a high % efficiency has a high amount of kinetic friction.

  14. Multiple Choice For a bicycle with seven rear-wheel gears and three pedal gears, the number of gear ratios possible is, • 7 + 3 = 10 • 7 - 3 = 4 • 7 / 3 = 7/3 • 7 x 3 = 21

  15. Multiple Choice If your head is initially bent downward, and then you raise it slowly, your neck is acting as a, • First-class lever • Second-class lever • Third-class lever • None of the above because the neck is not a lever

  16. Multiple Choice If a lever has an actual mechanical advantage of 0.5, then if can be, • A second-class lever only, • Either a first-class lever or a third-class lever • A third-class lever only • A first-class lever only

  17. Multiple Choice If a pair of gears has 12 teeth where the load is attached and 6 teeth where the effort force is applied, then the • IMA is 2 • IMA is 0.5 • AMA is 2 • AMA is 0.5

  18. Multiple Choice If the effort force is applied to the small axle of a wheel and axle, • The load force is decreased, but the load distance is increased • Both the load force and the load distance are increased • The load force is increased, but the load distance is decreased • Both the load force and the load distance are decreased

  19. Multiple Choice The IMAs of the two pulley systems are, • 4,4 • 5,4 • 4,5 • 5,5

  20. Multiple Choice On a multi-speed bike, you choose a pedal gear with 45 teeth and a rear-wheel gear with 15 teeth. You are likely • Riding up an incline into the wind • Riding down an incline with a tail wind • Moving slowly while pedalling quickly • Any of the above because the choice of gears depends only on the strength of the rider’s legs

  21. Multiple Choice If you were on one end of a seesaw that is between 2 m and 3 m long, the load torque caused by your body would be closest to • 10 Nm • 100 Nm • 1000 Nm • 10 000 Nm

  22. Multiple Choice The simple machines that make up the can opener are • Lever, wedge, inclined plane, gears • Lever, wedge, wheel and axle, gears • Pulley, wheel and axle, lever • Gears, pulleys, lever

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