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TRANSCRIPT: EXPLORE ACTIVITY -- 6.8 E: Inclined Planes and Pulleys

[Overview Statement]
[1-2] In this activity, students explore inclined planes and various pulleys to understand how simple machines can reduce the force needed to lift an object.

[Part I Title] Testing Inclined Planes
[3] Let’s explore inclined planes. [Or just…] Testing Inclined Planes.

[Title – Part 1: Materials (For Each Group In Your Class)]
[4] 20 marbles, 1 30-cm piece of heavy cotton twine, a stack of 5 hardcover books, 1 3-foot, smooth board, 1 plastic sandwich bag, and 1 250g/2.5N spring scale.

[5] As a preparatory note, place marbles inside a sandwich bag and seal. [6] Tie one end of the 30-cm string to the hook of the spring scale, and [7] the other end to the sandwich bag.

[Section 1]
[8] Break students into groups of 2 or 3 to examine objects in the classroom or [9] on the school grounds, and take digital photographs of any visible incline planes. Discuss the results of this exploration.

[Section 2]
[10] To begin, use the spring scale to measure and record the weight of the bag of marbles. [11] Next, stack five hardcover books at the end of a table. Then use the spring scale to lift the marble load from the table to the top of the stack of books. [12] Measure the amount of force required to raise the bag, and record the results in Newtons.
[Section 3]
[13] Now create an inclined plane with a 3-foot board. [14] Instead of hoisting the load, stand to the side and pull the marbles up the ramp. For a precise measurement, the string should be parallel to the board. [15] Repeat the action with different numbers of books. [16] Record the force required to transfer the marbles for each change in height.



[Part II Title] Playing With Pulleys
[17] Using pulleys to reduce the force needed to lift loads. [Or just…] Playing With Pulleys.

[Title – Part 2: Materials (For Each Group In Your Class)]
[18] 1 roll of duct tape, 1 metric ruler, 1 500g/5 N spring scale, 2 pulley wheels with hook or clip, 1 3-ft long by (a minimum of) 6 inches wide, smooth board, 2 1-ft long, 2x2, 2 eyehooks screws, 1 bag of sand, 1 16-ounce plastic cup, 1 single hole-puncher, 1 120-cm (about 1.2 m) piece of heavy cotton twine, and 1 200-ml beaker.

[19] In preparation, screw eyehooks to the ends of two 2x2’s. [20] Duct tape the wood to the edge of the table, setting them a foot apart, and allow the hooks to overhang. [21] To create the load, pour 200 ml of sand into a 16-ounce plastic cup. [22] Punch two holes on opposite sides of the rim. [23] Insert 20-cm of twine through the holes and tie a knot to form a handle; [24] for the remaining meter, form loops—one at each end—and tie or secure with duct tape. [25] Set out materials in plastic bins.

[Section 1]
[26] In order to measure the reduction of force needed to lift a cup of sand, we’ll construct three types of pulleys: Fixed, Moveable, and Block & Tackle.

[27] First, use the spring scale to measure the initial load weight of the plastic cup and record this measurement.

[28] For the single, Fixed pulley, hang a pulley wheel from one of the eyehooks. [29] Secure one end of the twine to the load handle, thread over the wheel and attach the other end to the spring scale. Pull downwards to lift the load off the ground. Record the force required to lift the cup.

[Section 2]
[30] To assemble a Moveable pulley, loop one end of the twine on the first 2x2 hook. [31] Attach a pulley wheel to the load handle. Thread the twine under the wheel and pull upwards with the spring scale to lift the cup of sand. Record the measurement.

[Section 3]
[32] Finally, use two pulley wheels for a Block & Tackle system, one attached to the second 2x2 hook and [33] the other mounted to the load handle. [34] Pass the twine between the two wheels to create a belt and lift the cup of sand using the spring scale. Again, record the measurement.

[35] As a last exercise, draw each pulley system and complete the remaining questions in the student journal.


Pulleys with scale, pulleys, how pulleys work, physics

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