MSE 803 LAB SIMPLE MACHINES
DIRECTIONS: For each of the following sections, begin by using the Essence of Simple Machines website, http://www.cosi.org/files/Flash/simpMach/sm1.swf , to answer the “pre-lab” questions. If necessary, use other websites that explain the use and operations of simple machines. Then, complete the lab activity.
SIMLE MACHINE 1: INCLINED PLANE
Pre-Lab: In the space below, draw in a free-body force diagram of an inclined plane. Also, show the input (effort) and output (resistance) forces acting on an object on the inclined plane, along with the equation for calculating the Mechanical Advantage of an inclined plane. Give two real life examples of an inclined plane.
Lab:
Materials
1-meter ramp meterstick friction block ring stand spring scale
4 100-g masses right angle clamp support rod
Procedure
1) Attach the 4 masses to the friction block. Weigh the block and masses with the spring scale. Record this measurement under ”Resistance” in Table 1.
2) Adjust the right-angle clamp so that the upper end of the ramp is 10 cm above the tabletop. This value, in meters, will be equal to the “Resistance Distance.”
3) Measure the length of the ramp in meters. Record this measurement as the “Effort Distance” in Table 1.
4) Put the friction block and masses on the ramp. Attach the spring scale to the friction block as shown.
5) Pull the block up the ramp at constant speed. While pulling, read the spring scale. Record your measurement under “Effort” in Table 1.
6) Change the ramp to 20 cm.
7) Repeat Steps 5 and 6.
8) Continue to repeat Steps 5 and 6 for ramp heights of 30 and 40 cm.
9) For each trial in Table 1, calculate the input and output work by using the following formulas and record your answers in Table 1:
a. Input = effort force x effort distance
b. Output = resistance force x resistance distance
10) To calculate the efficiency for each trial, us the following formula and record the efficiency for each trial in Table 1: efficiency = (output/input) x 100 = ______%
Table 1
Resistance Distance (m) / Effort Distance (m) / Resistance (N) / Effort (N) / Input Work (N-m) / Output Work (N-m) / Efficiency (&)0.10
0.20
0.30
0.40
Questions:
1. How did the effort force change as the resistance distance changed?
2. How did the efficiency of the machine change as the resistance distance changed?
3. Would you expect the mechanical advantage of this machine to be greater than, less than, or equal to 1? Why?
SIMPLE MACHINE 2: PULLEYS
Pre-Lab: In the space below, draw in a free-body force diagram of a pulley system. Also, show the input (effort) and output (resistance) forces acting on an object, along with the equation for calculating the Mechanical Advantage of a pulley system. Give two real life examples of a pulley system.
Lab:
Materials
2 single pulleys 2 double pulleys set of hooked masses spring scale
2 m of string meterstick
Procedure
1) Set up the single fixed pulley system, as shown.
2) Select a mass that can be measured on your spring scale. Record the mass in Table 1. Determine the weight, in Newtons (N), of the mass to be raised by multiplying its mass in kg by the acceleration due to gravity using the equation Fg=mg or F=(mass)(9.81 m/s2)
3) Carefully raise the mass by pulling on the spring scale. Measure the height, in meters, that the mass is lifted. Record this value in Table 1. Calculate he work output of the mass by multiplying its weight by the height it was raised. Record this value in Table 2.
4) Using the spring scale, raise the mass to the same height it was raised in step 3. Ask your lab partner to read, directly from the spring scale, the force, in Newtons, required to life the mass. (If your spring scale is calibrated in grams, rather than Newtons, calculate the force by multiplying the reading expressed in kilograms by gravity.) Record this value in Table 1 as the force of the spring scale. As you are lifting the load with the spring scale, pull upward at a slow, steady rate, using the minimum amount of force necessary to move the load. Any excess force will accelerate the mass and cause an error in your calculations.
5) Measure the distance in meters through which the force acted to lift the load to the height it was raised. Record this value in Table 1 as the distance, d, through which the force acts. Determine the work input in raising the mass by multiplying the force reading from the spring scale by the distance through which the force acted. Record the value for the work input in Table 2.
6) Repeat steps 2 through 5 for a different mass.
7) Repeat steps 2 through 6 for each of the different pulley arrangements in Figure A. Be sure to include the mass of the lower pulley(s) as pat of the mass raised.
8) Count the number of lifting strands of string used to support the weight or load for each arrangement, 1 through 4. Record these values in Table 2.
Table 1
Pulley arrangement / Mass Raised (kg) / Weight (Fg) of mass (N) / Height (h) mass is raised (m) / Force (F) of spring scale (N) / Distance (d) through which force acts (m)1
2
3
4
Table 2
Pulley arrangement / Work Output (Fg *h)(J) / Work Input (F*d)
(J) / IMA
(d/h) / Number of lifting strands / Efficiency %
1
2
3
4
Questions:
1. What are some possible reasons your efficiency is never 100%?
2. What happens to the input force (F) as the mechanical advantage gets larger?
3. How does increasing the number of pulleys affect the mechanical advantage of a pulley system?
4. Explain why the following statement is false: A machine reduces the amount of work you have to do. What does a machine actually do?
SIMPLE MACHINE 3: LEVERS
1ST CLASS LEVERS
Pre-Lab: In the space below, draw in a free-body force diagram of a 1st class lever. Also, show the input (effort) and output (resistance) forces acting on the lever and object, along with the equation for calculating the Mechanical Advantage of a 1st class lever. . Give two real life examples of a first class lever.
Lab:
Materials
Meterstick spring scale fulcrum wheel & block cord
4 100-g masses fulcrum support
Procedure
1) Hang the 4 100-g masses from the spring scale to determine their weight in Newtons. Record this value in Table 1 under “Resistance.” (The resistance will be the same for each trial.)
2) Set up the first-class lever as shown in your diagram. The fulcrum should be at the 20-cm mark on the meterstick, the resistance should be attached to the zero end of the meterstick, and the effort (spring scale) should be attached to the 100-cm end of the meterstick.
3) Pull upward on the spring scale and read the amount of effort required to the lift the resistance. Record your measurement under “Effort” in Table 1.
4) Adjust the lever so that the fulcrum is at the 30-cm mark. Repeat Step 3.
5) Continue repeating Step 3 with the fulcrum at 40 50, 60, 70 and 80 cm.
6) For each trial, use the formulas and record your answers in Table 1:
a. Ideal MA = effort arm /resistance arm
b. Actual MA = resistance force / effort force
Table 1
Effort arm (Cm) / Resistance Arm (cm) / Effort Force (N) / Resistance Force (N) / Ideal MA / Actual MA80 / 20
60 / 40
50 / 50
40 / 60
20 / 80
Questions:
1. How does a first class lever help you do work?
2. Where would you place the effort and resistance forces in a first class lever to have the greatest mechanical advantage?
2ND CLASS LEVERS
Pre-Lab: In the space below, draw in a free-body force diagram of a 2nd class lever. Also, show the input (effort) and output (resistance) forces acting on the lever and object, along with the equation for calculating the Mechanical Advantage of a 2nd class lever. . Give two real life examples of a second-class lever.
Lab:
Materials
Meterstick Fulcrum fulcrum support 4 100-g masses spring scale
Procedure
1) Hang the 4 100-g masses from the spring scale to determine their weight in Newtons. Record this value in Table 1 under “Resistance.” (The resistance will be the same for each trial.)
2) Set up the second-class lever as shown in your diagram. The fulcrum should be at the 0-cm mark on the meterstick, the resistance should be attached to the 10-cm mark of the meterstick, and the effort (spring scale) should be attached to the 100-cm end of the meterstick.
3) Pull upward on the spring scale and read the amount of effort required to the lift the resistance. Record your measurement under “Effort” in Table 1.
4) Move the resistance to the 20-cm mark on the meterstick. Repeat Step 3.
5) Continue repeating Step 3 with the fulcrum at 30, 40 50, 60, 70, 80 and 90 cm.
6) For each trial, use the formulas and record your answers in Table 1:
a. Ideal MA = effort arm /resistance arm
b. Actual MA = resistance force / effort force
Effort arm (Cm) / Resistance Arm (cm) / Effort (N) / Resistance (N) / Ideal MA / Actual MA100 / 10
100 / 30
100 / 50
100 / 70
100 / 80
100 / 90
Questions:
1. How does a second class lever work?
2. Where would you place the resistance force to make a lever that requires the least effort force?
3RD CLASS LEVERS
Pre-Lab: In the space below, draw in a free-body force diagram of a 3rd class lever. Also, show the input (effort) and output (resistance) forces acting on the lever and object, along with the equation for calculating the Mechanical Advantage of a 3rd class lever. Give two real life examples of a third class lever.
Lab:
Materials
Meterstick Fulcrum fulcrum support 3 100-g masses spring scale
Procedure
1) Hang the 3 100-g masses from the spring scale to determine their weight in Newtons. Record this value in Table 1 under “Resistance.” (The resistance will be the same for each trial.)
2) Set up the third-class lever as shown in your diagram. The fulcrum should be at the 0-cm mark on the meterstick, the resistance should be attached to the 100-cm mark of the meterstick, and the effort (spring scale) should be attached to the 90-cm end of the meterstick.
3) Pull upward on the spring scale and read the amount of effort required to the lift the resistance. Record your measurement under “Effort” in Table 1.
4) Move the resistance to the 80-cm mark on the meterstick. Repeat Step 3.
5) Continue repeating Step 3 with the fulcrum at 70, 60 50, 40, 30, and 20 cm.
6) For each trial, use the formulas and record your answers in Table 1:
a. Ideal MA = effort arm /resistance arm
b. Actual MA = resistance / effort
Effort arm (cm) / Resistance Arm (cm) / Effort (N) / Resistance (N) / Ideal MA / Actual MA90 / 100
70 / 100
50 / 100
30 / 100
Questions:
1. How is a third class lever used?
2. How can you construct a third-class lever with the greatest possible mechanical advantage?
3. If the mechanical advantage of a third class lever is less than 1, what is the benefit of using this type of lever?
AFTER COMPLETNG ALL THREE CLASSES OF LEVERS, YOU MAY COMPLETE THE LEVERS VENN DIAGRAM THAT FOLLOW THIS LAB
SIMPLE MACHINE 4: WHEEL AND AXLE
Pre-Lab: In the space below, draw in a free-body force diagram of a wheel and axle system. Also, show the input (effort) and output (resistance) forces acting on the wheel and axle, along with the equation for calculating the Mechanical Advantage of a wheel and axle system. Give two real life examples of a wheel and axle.
Lab:
Materials:
Meterstick screwdriver washers string
The screwdriver is an example of a simple machine called a Wheel & Axle. A simple machine is a
device that performs work by converting forces and distances. All simple machines have a characteristic called the
MECHANICAL ADVANTAGE (MA). The MECHANICAL ADVANTAGE can be obtained experimentally by building a Wheel & Axle and using the formula:
MA = Distance moved by the wheel / distance moved by the axle
The MA can also be calculated mathematically by using the formula:
MA = Diameter of the Wheel / Diameter of the Axle
In this lab, you build a Wheel & Axle, obtain the MA experimentally and mathematically and then compare the two results.
1. Attach one string weighted with washers to the Wheel (handle) of the screwdriver and another weight string to the
Axle (shaft) as shown below.
2. Hold the screwdriver so the weights hang straight down. Measure the length of each string and record in the “0
TURNS” box on the DATA TABLE.
3. Turn the screwdriver exactly 1 (one) turn. Measure the length of each string and subtract from the “0 TURNS”
measurement to determine how much string was wrapped around the Wheel (handle) and Axle (shaft). This value is the DISTANCE the Wheel and Axle have traveled. Record these values in the “1 TURN” box on the DATA TABLE.