Name ____________________________ Date _______________
Period _____
POE 1.1-10 Mechanisms Unit Review Answer Key MULTIPLE CHOICE: Choose the best response to the question and write the letter on the line provided.
B ____ 1)
The gear train at the right consists of a 40-tooth (input), 20-tooth, and 30-tooth (output) gear. If the input gear rotates 15 times, how many times will the output gear rotate? A.
10 times
C. 24 times
B ____ 2)
Seesaw
C. Tweezers
always greater than 1
C. always equal to 1.
____ 5) A
D. 30 times
B.
Wheelbarrow
D. Pliers
In a 3rd class lever, the mechanical advantage is A.
D ____ 4)
20 times
out
A example of a 2nd class lever is a A.
D ____ 3)
B.
nout in nin out
B.
15 40 30
20
resistance force is located between the effort force and the fulcrum by definition
sometimes greater than 1.
D. always less than 1.
The wheels on a car are 24 inches in diameter. In order for the car to travel exactly 200 feet (assuming no skidding or slipping), the wheel would need to revolve approximately A.
2.65 times
B.
8.33 times
C.
24.2 times
D.
31.8 times
200 ft 12in 2400 31.8 24 in 1 ft 75.4
When used to drive a screw, a screwdriver functions as A.
a wheel and axle
C. a screw
B.
an inclined plane
D. a lever
the handle is the wheel, and the shaft is the axle
B ____ 6)
If the pulley system (shown at the right) is lifting a 40 lb load, what is the minimum amount of effort that must be applied to the system? A.
8 lb
B.
C. 20 lb
10 lb
40 lb 10 lb 4
D. 40 lb
4 load-bearing strands IMA B ____ 7)
The engineering discipline that involves planning, researching, designing, manufacturing, and maintaining devices that produce or consume power is known as A.
Industrial engineering
B.
C. Electronic engineering
C ____ 8)
D. Environmental engineering
In the belt and pulley system shown at the right, Pulley A has a diameter of 5 in, Pulley B has diameter of 8 in, and Pulley C has a diameter of 9 in. If Pulley A is delivering 80 ft-lb of torque, then Pulley C is receiving approximately A.
80 ft-lb of torque
B.
128 ft-lb of torque
C.
144 ft-lb of torque
D.
400 ft-lb of torque
dout out d in in
C ____ 9)
Mechanical engineering
C
dC A dA
C
9 in 80 ft-lb 5 in
A
144 ft-lb
In physics, work is A.
actual divided by ideal
C. force times distance
B.
D. something to be avoided
B ____ 10) Ideal mechanical advantage is based on A.
effort and resistance forces
B.
effort and resistance distances
C.
inquiry-based calculations
D.
static equilibrium
effort minus resistance
B
C
Free Response: For each of the following problems, be sure to answer each question completely and to show all of your work. All answers should be accurate to three significant digits, and include units where appropriate. 11)
A screwdriver is used to pry open a can of paint, as shown at the right. When it is inserted in place, the length from the outside edge of the can to the tip of the screwdriver is 1 inch. The total length of the screwdriver is 8 inches. The lid on the paint can is providing 100 lb of resistance. a.
Illustrate and annotate the lever system described above (including the type of lever) FE 100 lb
1 in b.
What is the ideal mechanical advantage of the system?
IMA
c.
12)
first class lever
7 in
DE DR
IMA
7 in 7 1 in
Using static equilibrium calculations, calculate the effort force needed to overcome the resistance force in the system. 1 in 100 lb DE FE DR FR 7 in FE 1 in 100 lb FE 14.3 lb 7 in
A civil engineer must design a wheelchair accessible ramp next to a set of steps leading up to a building. The height from the ground to the top of the stairs is 18 in. Based on ADA codes, the slope must be 1:10 or less. Slope is equal to the rise of the ramp divided by the run of the ramp. a.
Using the ADA code, what is the allowable minimum length of the ramp base? 1 18 in 10 x
x 10 18 in 180 in or 15 ft
b. Using the known height and calculated base length, what is the length of the slope of the ramp?
a2 b2 c 2 c.
What is the ideal mechanical advantage of the ramp?
IMA
d.
c 182 1802 32724 181 in
DE DR
IMA
181 in 10.1 18 in
If a person and wheelchair have a combined weight of 260 lb, how much ideal effort force is required to travel up the ramp? (In other words, assuming that AMA IMA , what is FE ?) F 260 lb 260 lb AMA R 10.1 FE 25.7 lb 10.1 FE FE
13)
A 12 inch adjustable crescent wrench is tightening a 5/8 24 UNC bolt into a mechanical assembly. a.
Assuming the effort is applied at the end of the wrench, determine the circumference of the effort force.
circumference 2 r 2 12 in 75.4 in b.
Determine the pitch of the screw.
c.
1 1 0.042 in threads per inch 24 What is the ideal mechanical advantage gained in the system? pitch
DE 75.4 in IMA 1795 0.042 in DR If 15 lb of effort force is required to turn against 1875 lb of resistance, what is the actual mechanical advantage? IMA
d.
AMA e.
FR FE AMA IMA
efficiency
125 0.070 or 7.0% 1795
A 32 inch diameter wheel is driving a 5 inch axle. The wheel is providing 130 pounds of force, whild the axle is providing 700 pounds of force. What is the IMA, AMA, and efficiency of this wheel and axle system? IMA
IMA
DE DR
32 in 5 in 6.40
15)
1875 lb 125 15 lb
What is the efficiency of the screw?
efficiency
14)
AMA
AMA
AMA
FR FE
efficiency
AMA IMA 5.38 6.40 .841 or 84.1%
efficiency
700 lb 130 lb 5.38
Name the 17 engineering disciplines that the U.S. Government keeps statistics on.
Aerospace Agricultural Biomedical Chemical Civil Computer Hardware
Electrical Electronics
Materials
Envionmental Health and Safety
Mining and Geological Nuclear
Industrial Marine and Ocean
Petrolem
Mechanical
