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. F , T

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 C

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. T F

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 B

Multiple Choice The IMA of the handgrip is 3 1/3 4 1/4 A

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. T F

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 A

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. T T

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 D

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. F F

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 C

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. T F

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 D

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 C

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 B

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 B

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 A

Multiple Choice The IMAs of the two pulley systems are, 4,4 5,4 4,5 5,5 C

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 B

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 C

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 B