Materials Included In Kit

Additional Materials Required

Safety Precautions

The materials in this lab are considered nonhazardous. Use care when adding and removing masses to the slotted weight hanger. Do not allow the masses to drop on the floor. Please follow all other laboratory safety guidelines.

Disposal

The materials should be saved and stored for future use.

Lab Hints

• Enough materials are provided in this kit for eight student groups.
• Spring scales can be used instead of hanging masses. In order to determine the necessary force needed to raise the Hall’s carriage, students must pull on the spring scale at a constant speed. When the carriage is being raised with a constant speed, the force registered on the spring scale will remain relatively constant (the pulling force and force due to gravity will be balanced). Students should record the force on the spring scale only when the carriage is moving at a constant speed.
• Textbooks can be placed under the support stand in order to raise it high enough to achieve the 45° or higher angles. If a tall support stand is used, textbooks may not be necessary.
• Additional experiments can be performed with this inclined plane, such as friction experiments, rolling experiments and projectile motion. The Friction Blocks Set, AP6222, Ring and Discs, AP4634, Variable Inertia Kit, AP4633, and Projectile Motion with an Inclined Plane, AP6755, are excellent accessories that can be used with the inclined planes provided in this kit. These kits are available through Flinn Scientific, Inc.

Sample Data

Distance between start line and finish line: ___23.60 cm___
Mass of Hall’s carriage: ___101.1 g___
Additional mass added to Hall’s carriage: ___100 g___

Results Table
Weight of Hall’s carriage plus any additional mass: ___1.97 N___

Answers to Questions

1. For each inclined plane angle, determine the force necessary to raise the Hall’s carriage. Multiply the Mass Needed to Raise Hall’s Carriage (in kilograms) by the acceleration due to gravity constant, 9.81 m/s². The resulting force will have units called newtons (N). Enter these calculations, as well as the units, in the results table.

   Also, multiply the mass of the Hall’s carriage plus additional mass (in kilograms) by the acceleration due to gravity constant to determine the weight of the carriage. Record this in the results table.

   Sample calculations:

   68 g x (1 kg/1000 g) x 9.81m/s² = 0.67 N

   201.1 g x (1 kg/1000 g) x 9.81 m/s² = 1.97 N

2. Use Equation 2 to calculate the ideal mechanical advantage for each experimental angle of the inclined plane. Record this information in the results table.

   Sample calculation:

   23.60 cm/(21.00 cm – 8.70 cm) = 1.92

3. Use Equation 1 to calculate the actual mechanical advantage for each experimental angle. Record this information in the results table.

   Sample calculation:

   1.97 N/0.67 N = 2.94

4. Calculate the amount of energy that was needed to raise the carriage for each inclined plane angle. To do this, multiply the force needed to raise the carriage at a specific angle by how far the carriage traveled along the inclined plane (in meters). The resulting energy will have units called joules (J). Record these calculations, including units, in the results table.

   Sample calculation:

   0.67 N x 0.236 m = 0.16 J

5. Calculate the “ideal” energy required to raise the carriage from the start line height to the finish line height by multiplying the weight of the Hall’s carriage by total height the carriage was raised. Record this in the results table.

   Sample calculation:

   1.97 N x (26.95 cm – 10.80 cm) x (1 m/100 cm) = 0.318 J

6. What angle of the inclined plane made raising the Hall’s carriage the easiest?

   The smallest angle (16.0°) required the least amount of force to raise the Hall’s carriage.

7. How does the mechanical advantage compare to the ease of raising the Hall's carriage?

   The larger the mechanical advantage, the easier it is to raise the Hall’s carriage. More force is required to lift the Hall’s carriage when the mechanical advantage is small.

8. What is an advantage of an inclined plane?

   An advantage of a simple machine is that it helps reduce the force needed to raise a heavier object.

9. What is a disadvantage of an inclined plane?

   The disadvantage of a simple machine is that, although a smaller force is required, the force must be applied over a longer distance compared to how far (or high) the object moves.

10. Explain why the energy required in each case is similar to the “ideal” energy even though the needed force was less than the weight of the carriage. If any “extra” energy was needed to raise the carriage up the inclined plane, compared to the ideal case, why was it needed?

    The energy required to raise the Hall’s carriage with an inclined plane was similar to the ideal case of simply lifting the carriage straight up because the force used to raise the carriage to a certain height was used for a longer distance along the inclined plane. The energy was a force multiplied by the distance. For each case, the actual energy required was slightly larger than the ideal case. It required more energy to raise the carriage using the inclined plane because “extra” energy was needed to overcome the forces of friction in the wheels of the carriage and in the spinning pulley.

11. Based on the results of this lab, what would be the best position of a ramp used to raise a 500-lb motorcycle into the back of a truck in the easiest possible way?

    In order to raise a motorcycle into the back of a truck with the least amount of force, a ramp must be used in such a way as to have the smallest angle with respect to the ground. The longer the ramp, the smaller the angle and the easier it will be to raise the motorcycle.

Introduction

The problem: A piano needs to be lifted onto a moving truck. The piano is too heavy to lift straight up. How is it possible to move the piano onto the truck without breaking it into many lighter pieces? In this experiment this question will be answered by studying one type of simple machine—the inclined plane.

Concepts

• Simple machines
• Mechanical advantage
• Inclined plane

Background

A simple machine is a piece of equipment that changes the size or direction of an applied force. Examples of simple machines include pulleys, screws, gears, levers and wedges. These devices may appear “simple,” but by grouping various simple machines together, very “complex” machines can be created, such as engines or cranes. An inclined plane is another example of a simple machine. An inclined plane is more commonly referred to as a ramp.

Simple machines are useful because they reduce the amount of force needed to move or lift an object. Simple machines provide the means for a normal person to lift a two-thousand pound car in order to change a tire (using a car jack). Simple machines can also be used by a 200-lb man to move a two-ton boulder (using a lever). The comparison between how much force is applied to how much force (weight) is moved is referred to as the mechanical advantage of the simple machine. For example, a simple machine that has a mechanical advantage of five will provide five times more lifting force compared to the applied force. That is, 100 lbs of applied force can lift a 500-lb object. The mechanical advantage of a simple machine is determined by calculating the ratio of the force required to move the object without the assistance of a simple machine to the actual force applied to the simple machine (Equation 1).

A simple machine does not provide “extra force” for free without something in return. A simple machine with a mechanical advantage of five will provide five times more lifting force compared to the force that is applied. However, the smaller applied force must be used over a distance that is five times farther than the distance the heavier object moves. The ideal mechanical advantage of a simple machine is determined by comparing how far the applied force moves to how far the object moves. It is considered “ideal” because it is based only on distances. Actual mechanical advantage must account for the force needed to overcome friction, as well as other factors. Therefore, actual mechanical advantage will always be less than the ideal mechanical advantage. For the inclined plane, the ideal mechanical advantage can be calculated using Equation 2.

Experiment Overview

In this experiment, determine the mechanical advantage of an inclined plane that is positioned at different angles.

Materials

Safety Precautions

The materials in this lab are considered nonhazardous. Use care when adding and removing masses to the slotted weight hanger. Do not allow the masses to drop on the floor. Please follow all other laboratory safety guidelines.

Procedure

Preparation

1. Obtain the wood inclined plane, pulley, wing nuts, screws and washers.
2. Secure the pulley to the inclined plane as shown in Figure 1.
   {12569_Preparation_Figure_1}

 Experiment

1. Obtain an assembled inclined plane, a pencil and a ruler.
2. At the end opposite to the pulley, measure approximately 12 cm from the end of the board and lightly mark this point with a pencil. The mark should be far enough from the end of the inclined plane so that all four wheels of the Hall’s carriage are on the inclined plane when the front of the carriage lines up with this mark.
3. Use a ruler to make a light pencil line through this 12-cm mark so the line is parallel to the end of the Board (see Figure 2). This line represents the “start line.”
   {12569_Procedure_Figure_2}
4. At the pulley end, measure approximately 7 cm from the end of the board and lightly mark this point with a pencil.
5. Repeat step 3 to draw the “finish line.”
6. Use a meter stick or ruler to measure the distance between the start line and the finish line. Record this distance in the data table.
7. Obtain a Hall’s carriage and thin string.
8. Measure the mass of the carriage to the nearest gram using a balance. Record the mass in the data table.
9. Measure and cut approximately 60 to 80 cm of string.
10. Tie one end of the string to the front of the carriage.
11. Tie the other end of the string to a slotted weight hanger.
12. Set up the inclined plane as shown in Figures 2 and 3. The starting angle should be approximately 15° with respect to the tabletop.
    {12569_Procedure_Figure_3}
13. Measure the exact angle of the inclined plane with respect to the ground using a protractor. Record this angle in the data table.
14. Measure the height of the start line from the tabletop. Record this height in the data table (see Figure 3).
15. Measure the height of the finish line from the tabletop. Record this height in the data table (see Figure 3).
16. Place the Hall’s carriage at the base of the inclined plane and hang the string over the pulley so that the slotted weight hanger hangs over the edge of the table (see Figure 3). Note: If the mass of the slotted weight hanger is heavy enough to move the Hall’s carriage up the inclined plane, add 100-g to the Hall’s carriage to make it heavier than the slotted weight hanger. Record the amount of additional mass in the data table.
17. Start with the front of the Hall’s carriage at the start line as shown in Figure 3.
18. Carefully add slotted masses to the slotted weight hanger in 10-g increments until the carriage just begins to travel up the inclined plane.
19. Once the carriage begins to move, remove the last 10-g mass that was added.
20. Move the Hall’s carriage back to the start line.
21. Add slotted masses in 1- or 2-g increments until the carriage just begins to move up the inclined plane. When it appears that the carriage is about to move, give the carriage a small nudge with a finger to overcome the initial frictional forces (static friction). After the small nudge, if the carriage stops, add an additional mass to the weight hanger. If it continues to move up the inclined plane, this is the minimum weight needed to raise the carriage.
22. Stop the carriage when the front of the carriage crosses the finish line.
23. Record the total mass of the slotted masses, including the mass of the hanger, needed to just move the Hall’s carriage up the inclined plane.
24. Carefully lower the carriage to the base of the inclined plane and remove the slotted masses.
25. Increase the angle of the inclined plane to approximately 30°.
26. Repeat steps 13–25. Use the same Hall’s carriage and any additional masses that were needed for the first trial.
27. Increase the angle of the inclined plane to approximately 45°.
28. Repeat steps 13–25. Use the same Hall’s carriage and any additional masses that were needed for the first trial.
29. Consult your instructor for appropriate storage procedures.

Student Worksheet PDF

12569_Student1.pdf