Transcript Mechanical Systems

Mechanical
Systems
Review
March 2010
True/False
1. When you use your thumb and index
finger to pull up your socks, you are using
a first-class lever.
2. For a third-class lever, the load force
always exceeds the effort force.
Multiple Choice
When arm-wrestling, your arm is acting as
a) A first-class lever
b) A second-class lever
c) A third-class lever
d) None of these because the arm cannot be
a lever
True/False
1. To make the toy top spin, you spin the
axle, creating a speed advantage for the
wheel.
2. Torque and ideal mechanical advantage
are measured in newton-metres.
Multiple Choice
The exercise handgrip is
a) A first-class lever
b) A second-class lever
c) A third-class lever
d) Either a second-class lever or a thirdclass lever, depending on where the
fulcrum is considered to be
Multiple Choice
The IMA of the handgrip is
a) 3
b) 1/3
c) 4
d) 1/4
True/False
1. If the effort distance for a machine part is
greater than the load distance, then the
machine provides a force advantage.
2. Scissors are an example of a secondclass lever combined with an inclined
plane.
Multiple Choice
For any machine, as the friction of the
moving parts increases,
a) The AMA and the % eff decrease
b) The AMA and the % eff increase
c) The AMA increases but the % eff
decreases
d) The AMA decreases but the % eff
increases
True/False
1. In the equation for torque, the force F is
perpendicular to the rigid object.
2. To obtain a force advantage for a wheel
and axle, the effort force must be applied
to the wheel.
Multiple Choice
As the angle of a wheelchair ramp changes
from 10° to 20°,
a) The effort force falls and the AMA rises
b) Both the effort force and the AMA rise
c) Both the effort force and the AMA fall
d) The effort force rises and the AMA falls
True/False
1. To increase the force of a machine, the
distance from the fulcrum must be
decreased.
2. The torque on a rigid object is greater
when the applied force is parallel to the
rigid object.
Multiple Choice
When using a hammer to remove a nail from a
board,
a) The hammer acts as a third-class lever with
an AMA greater than one
b) The hammer acts a second-class lever with
an AMA greater than one
c) The hammer acts as a first-class lever with
an AMA greater than one
d) None of the above
True/False
1. In any machine that experiences friction,
the ideal mechanical advantage exceeds
the actual mechanical advantage.
2. A machine with a high % efficiency has a
high amount of kinetic friction.
Multiple Choice
For a bicycle with seven rear-wheel gears
and three pedal gears, the number of gear
ratios possible is,
a) 7 + 3 = 10
b) 7 - 3 = 4
c) 7 / 3 = 7/3
d) 7 x 3 = 21
Multiple Choice
If your head is initially bent downward, and
then you raise it slowly, your neck is acting
as a,
a) First-class lever
b) Second-class lever
c) Third-class lever
d) None of the above because the neck is
not a lever
Multiple Choice
If a lever has an actual mechanical
advantage of 0.5, then if can be,
a) A second-class lever only,
b) Either a first-class lever or a third-class
lever
c) A third-class lever only
d) A first-class lever only
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
a) IMA is 2
b) IMA is 0.5
c) AMA is 2
d) AMA is 0.5
Multiple Choice
If the effort force is applied to the small axle of a
wheel and axle,
a) The load force is decreased, but the load
distance is increased
b) Both the load force and the load distance are
increased
c) The load force is increased, but the load
distance is decreased
d) Both the load force and the load distance are
decreased
Multiple Choice
The IMAs of the two pulley systems are,
a) 4,4
b) 5,4
c) 4,5
d) 5,5
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
a) Riding up an incline into the wind
b) Riding down an incline with a tail wind
c) Moving slowly while pedalling quickly
d) Any of the above because the choice of
gears depends only on the strength of the
rider’s legs
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
a) 10 Nm
b) 100 Nm
c) 1000 Nm
d) 10 000 Nm
Multiple Choice
The simple machines that make up the can
opener are
a) Lever, wedge, inclined plane, gears
b) Lever, wedge, wheel and axle, gears
c) Pulley, wheel and axle, lever
d) Gears, pulleys, lever