University of Arkansas - AgriScience Project

AGRISCIENCE EXERCISE

PHYSICAL SCIENCES IN AGRICULTURE

Key Concept: Energy & Power Systems

Sub-Concept: Power Transmission

Agricultural Application: The agricultural industry relies on the efficient transmission of power in mechanical systems.

Exercise: Determining the Mechanical Advantage and Efficiency of a Hydraulic System

Applied Principle(s): Basic principles of hydraulics

Goals:

  1. Describe the principles and applications of hydraulic power transmission.
  2. Calculate the actual and theoretical mechanical advantage of a hydraulic system.
  3. Determine the efficiency of a hydraulic system.
  4. Describe the relationship between force, pressure, and area in a hydraulic system.


Materials: (per group)



References: Refer to any high school physics or mechanics textbook

Procedures for Conducting the Activity:

1. Divide the class into pairs of students, and provide each with a data sheet and the necessary materials for this exercise.

2. Instruct the students to complete the activity as directed on the data sheets. You may wish to monitor their progress as they work; it is suggested that the students be left to follow the instructions and complete the activity on their own.

3. When all groups have completed the exercise, review the discussion questions as a class, noting the agricultural applications of the principles demonstrated.









AGRISCIENCE EXERCISE

- Determining Mechanical Advantage and Efficiency of a Hydraulic System -

Student Data/Information Sheet

1. Gather the following materials:

2. Fill the model with water. Be sure to eliminate all air bubbles from the system. (The presence of air, a compressible substance, in a hydraulic system greatly reduces system performance.)

3. Balance an object of known weight (5 to 10 lbs.) on the plunger of the large syringe.

4. Slowly pull downward on the spring scale and record the amount of force required to raise the plunger of the large syringe. Record your measurement below.

Force = __________

5. Calculate the actual mechanical advantage of the hydraulic system using the following formula.

Actual Mechanical = Force exerted by large plunger (wt. of load)

Advantage Force exerted on small plunger x 2*

Actual Mechanical Advantage = __________

*Note: The handle of the hydraulic system model is a second class lever that produces a 2:1 mechanical advantage. Since we are interested in the mechanical advantage produced by the hydraulic system only, the "2" is included in the denominator to cancel out the lever's mechanical advantage.

6. Determine the theoretical mechanical advantage of the hydraulic system.

a. Determine the area (in2) of the large plunger using the following formula.

Area, in2 = pr2 where p = pi, which is equal to 3.1416

r = radius of plunger

Record the area of the large plunger here: __________

b. Determine the area of the small plunger using the same formula as in 6A. Area of small plunger: __________

c. Calculate the theoretical mechanical advantage using the following formula.

Theoretical Mechanical = Area of large plunger

Advantage Area of small plunger

Theoretical Mechanical Advantage = __________

7. Calculate the efficiency of the hydraulic system using the following formula.

Efficiency (e) = Actual mechanical advantage x 100

Theoretical mechanical advantage

Efficiency (e) = __________%

8. Determine the relationship between force, pressure, and area in the hydraulic system.

a. Place the weight on the large plunger.

b. Apply just enough force to the small plunger to balance the weight.

c. With the weight balanced, read the pressure gauge.

Pressure = __________psi

d. Divide the weight of the load by the area (in2) of the large plunger (obtained in Step 6a).

lbs. = psi

___in2

e. Compare the calculated pressure (8d) to the measured pressure (8c). If there is a difference, can you explain why?















9. Answer the following discussion questions. Be prepared to share your results with the class.

a. Define "efficiency" as it relates to the performance of a hydraulic system.

















b. What factors prevent a hydraulic system from operating at 100% efficiency?

















c. How is efficiency related to actual mechanical advantage and theoretical mechanical advantage?

















d. What is the relationship between force, pressure, and area in a hydraulic system?





























Report any problems, comments or suggestions to the Webmaster.

This activity has been accessed content-type: text/html Could not get HTTP_REFERER Exitting times.