Answers
Activity 1.1.2 Simple Machines Practice
Problems
Procedure
Answer the following questions regarding simple machine systems. Each question
requires proper illustration and annotation, including labeling of forces, distances,
direction, and unknown values. Illustrations should consist of basic simple machine
functional sketches rather than realistic pictorials. Be sure to document all solution
steps and proper units. All measured values contain three (3) significant digits.
All problem calculations should assume ideal conditions and no friction loss.
Simple Machines – Lever
A first class lever in static equilibrium has a 50lb resistance force and 15lb effort
force. The lever’s effort force is located 4 ft from the fulcrum.
1. Sketch and annotate the lever system described above.
2. What is the actual mechanical advantage of the system?
Formula
Substitute / Solve
Final Answer
3. Using static equilibrium calculations, calculate the length from the fulcrum to the
resistance force.
Formula
Substitute / Solve
Final Answer
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A wheel barrow is used to lift a 200 lb load. The length from the wheel axle to the
center of the load is 2 ft. The length from the wheel and axle to the effort is 5 ft.
4. Illustrate and annotate the lever system described above.
5. What is the ideal mechanical advantage of the system?
Formula
Substitute / Solve
Final Answer
6. Using static equilibrium calculations, calculate the effort force needed to overcome
the resistance force in the system.
Formula
Substitute / Solve
Final Answer
A medical technician uses a pair of four inch long tweezers to remove a wood sliver
from a patient. The technician is applying 1 lb of squeezing force to the tweezers. If
more than 1/5 lb of force is applied to the sliver, it will break and become difficult to
remove.
7. Sketch and annotate the lever system described above.
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8. What is the actual mechanical advantage of the system?
Formula
Substitute / Solve
Final Answer
9. Using static equilibrium calculations, calculate how far from the fulcrum the
tweezers must be held to avoid damaging the sliver.
Formula
Substitute / Solve
Final Answer
Simple Machines – Wheel and Axle
10. What is the linear distance traveled in one revolution of a 36 in. diameter wheel?
Formula
Substitute / Solve
Final Answer
An industrial water shutoff valve is designed to operate with 30 lb of effort force. The
valve will encounter 200 lb of resistance force applied to a 1.5 in. diameter axle.
11. Sketch and annotate the wheel and axle system described above.
12. What is the required actual mechanical advantage of the system?
Formula
Substitute / Solve
Final Answer
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13. What is the required wheel diameter to overcome the resistance force?
Formula
Substitute / Solve
Final Answer
Simple Machines – Pulley System
A construction crew lifts approximately 560 lb of material several times during a day
from a flatbed truck to a 32 ft rooftop. A block and tackle system with 50 lb of effort
force is designed to lift the materials.
14. What is the required actual mechanical advantage?
Formula
Substitute / Solve
Final Answer
15. How many supporting strands will be needed in the pulley system?
Formula
Substitute / Solve
Final Answer
A block and tackle system with nine supporting strands is used to lift a metal lathe in
a manufacturing facility. The motor being used to wind the cable in the pulley system
can provide 100 lb of force.
16. What is the mechanical advantage of the system?
Formula
Substitute / Solve
Final Answer
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17. What is the maximum weight of the lathe?
Formula
Substitute / Solve
Final Answer
Simple Machines – Inclined Plane
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 2 ft.
Based on ADA codes, the slope must be 1:12 or less. Slope is equal to the rise of
the ramp divided by the run of the ramp.
18. Sketch and annotate the inclined plane described above.
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19. Using the ADA code, what is the allowable minimum length of the ramp base?
Formula
Substitute / Solve
Final Answer
20. Using the known height and calculated base length, what is the length of the slope
of the ramp?
Formula
Substitute / Solve
Final Answer
21. What is the ideal mechanical advantage of the ramp?
Formula
Substitute / Solve
Final Answer
22. If a person and wheelchair have a combined weight of 185 lb, how much ideal
effort force is required to travel up the ramp?
Formula
Substitute / Solve
Final Answer
Simple Machines – Wedge
A hydraulic shear applies a 2000 lb force to a wedge. It is used to shear plate steel
to rough size. The shear has a ¼ inch thick cutting blade with a 45 degree slope.
(Note 45°, 45°, 90° triangle)
23. Sketch and annotate the wedge described above.
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24. What is the length of the slope?
Formula
Substitute / Solve
Final Answer
25. What is the ideal mechanical advantage of the wedge?
Formula
Substitute / Solve
Final Answer
Simple Machines – Screw
A 7/16 nut driver with a 1 1/2 inch diameter handle is used to install a ¼ 20 UNC bolt
into a robotic arm.
26. Sketch and annotate the screw system described above.
27. Determine the circumference where the effort is applied.
Formula
Substitute / Solve
Final Answer
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28. Determine the pitch of the screw.
Formula
Substitute / Solve
Final Answer
29. What is the mechanical advantage gained in the system?
Formula
Substitute / Solve
Final Answer
30. How much force can be overcome if 5 lb of force is exerted?
Formula
Substitute / Solve
Final Answer
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