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Work and Simple Machines

Investigation 5 – Lab

Back to Investigation 5

BE PREPARED

Group materials:

2 100 g mass weights
3 meter sticks
1 5 Newton spring scale
1 small accessory box (or stack of books about 8 cm in height)
1 plastic bucket with handle
15 cm masking tape

Individual materials:

1 Student Data Record

Teacher Preparation

1. Organize the required materials at a distribution point.

2. Separate the class into five (5) groups.

Instruction

Each student group should obtain the following necessary materials from the distribution point: two (2) 100 gram mass weights, three (3) meter sticks, one (1) spring scale, one (1) small accessory box, one (1) plastic bucket with handle, one (1) 15 cm length of masking tape

Procedure:

In this Investigation, you will explore another simple machine, the inclined plane.

GET FOCUSED

During this part of the Investigation, students will investigate the results of varying the position of applied force on a lever when lifting a load.

They will also investigate the differences in the force required to lift a load as the length of the effort arm is changed by varying the position of the fulcrum along the lever.

INVESTIGATE

Trial 1

In Trial 1, you will determine the amount of force needed to lift a load 8 cm without using an inclined plane. Your determination of effort in this Trial will serve as a reference point for comparison of the effort used to lift the load the same height with and without the inclined plane.

Calibrate the spring scale if necessary.
Place 2 100 gram mass weights inside the white bucket.
Place the load on the hook of the spring scale.
Hold the spring scale so that the bucket rests on the table.
Place a meter stick with the 0 cm end on the table beside the bucket.
Lift the load until the bottom of the bucket is level with the 8 cm mark of the meter stick.

How much force did you exert to lift the load?

Trial 2

During Trial 2, you begin your exploration of the inclined plane. As a result of comparing Trials 1 and 2, you should come to understand that there is a difference in the force used to lift a load directly off the ground as opposed to lifting the load the same height through the use of an inclined plane. You will measure the effort needed to move the load up an inclined plane that is 8 cm high by pulling the load with a spring scale at a steady, constant pace.

The length of the inclined plane is the distance between the 0 cm mark on the meter sticks and the point where the meter sticks touch the small accessory box (or books). The length is NOT the entire length of the meter sticks. To begin your experiment, you will be presented with the following question and asked to make a prediction:

Will an inclined plane change the amount of effort needed to lift a load 8 cm off of the ground?

a. Record your prediction in Problem 2a in your Student Data Records.

b. Follow your Student Data Record to create and test an inclined plane.

Set a stack of books approximately 8 cm in height or the small accessory box upside down on the table.
Place two meter sticks on top of the small accessory box (or books).
The 80 cm mark of each meter stick should be resting on the edge of the accessory box (or books). The meter sticks should be parallel to each other (see figure below).
Move the meter sticks so there is a 4 cm space between them.
Masking tape may be applied at the 0 cm mark to hold the meter sticks in place.

Determine the height of the inclined plane (the height of the box or books) and record the height in centimeters and meters in Problem 2c in your Student Data Records.
Place the bucket so that its back end is resting on the 0 cm marks of both meter sticks.
Insert the hook of the spring scale through the hole in the bucket’s handle.
Use the spring scale to pull the bucket up the ramp at a steady, constant speed. The spring scale should be parallel with the meter sticks.

Pull the bucket over a length of 80 cm. Do this by pulling the bucket until its front end is at the 80 cm mark.
Observe the force shown on the spring scale as the bucket is moving. This is the effort force.
Record the effort force in your Student Data Record.

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Trials 3 and 4

You will continue your exploration of the inclined plane in Trials 3-4. Trials 1 and 2 were designed to allow you to observe that when an object is lifted to the same height with an inclined plane, as compared to without an inclined plane, the effort needed to move the object is reduced. In Trials 3 and 4, you will discover that the effort to lift a load to the same height is reduced when an inclined plane is used because the distance over which the effort is applied increases.

For example, in Trial 1, you lifted the load 8 cm above the table. The effort was applied over a distance of 8 cm. However, in Trial 2, the load was pulled 80 cm along the inclined plane, although the ending point of the load was still 8 cm above the ground. The effort applied was less, but the distance over which it was applied was greater than in Trial 1 (8 cm straight up).

You will continue to explore this concept by changing the steepness of the inclined plane and determining the effect the change in steepness has on the effort applied and work done to move the load. You will do this by varying the length, but not the height of the inclined plane and measuring the effort needed to pull the load along the length of each inclined plane.

You will be presented with questions before beginning these Trials and you will be asked to make two predictions.

Trial 3

Make two predictions:

Will decreasing the length but not the height of an inclined plane change the amount of effort required to lift the bucket?

Will decreasing the length, but not the height of an inclined plane change the amount of work needed to lift the bucket 8 cm off the table?

Record your predictions in Problem 4a in your Student Data Records then proceed with the Trial:

Reposition the meter sticks so that that the 70 cm mark of both sticks is resting on the edge of the accessory box or book stack.

Determine the height of the inclined plane at the 70 cm mark and record in Problem 4c in your Student Data Record.
Compare the steepness of the incline and answer
Use the spring scale to pull the bucket. Stop when the bucket is at the 70 cm mark. Observe the force shown on the spring scale as the bucket is moving and record the data in Problems 4f-h of your Student Data Record.

Trial 4

Consider two questions in Trial 4 as you proceed with the Trial and complete the lab:

Will decreasing the length but not the height of an inclined plane change the amount of effort required to lift the bucket?

Will decreasing the length, but not the height of an inclined plane change the amount of work needed to lift the bucket 8 cm off the table?

Decrease the length of the inclined plane to 60 cm.

Reposition the meter sticks so that that the 60 cm mark of both sticks is resting on the edge of the accessory box or books.
Determine the height of the inclined plane at the 60 cm mark.
Use the spring scale to pull the bucket. Stop when the bucket is at the 60 cm mark. Observe the force shown on the spring scale as the bucket is moving and record the data in Problems 5f-h of your Student Data Records.