Teacher Portal:
Earth’s Forces
Investigation 5 – Lab
BE PREPARED
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Teacher Preparation
- Place all materials at the distribution center.
- Divide the class into five (5) cooperative groups.
Instruction
- Direct each student group to obtain the following necessary materials from the distribution point: one (1) triple beam balance, one (1) spring scale, one (1) white bucket, two (2) sheets of sandpaper, one (1) wood block one, one (1) small thick elastic band, one (1) 100 g weight, one (1) roll of masking tape, and two (2) 30 cm plastic rulers.
GET FOCUSED
- Students will perform experiments to explore the effect of forces and mass on acceleration.
- Students will measure forces with a spring scale.
- As students perform their lab experiments, they should keep the following question in mind:
INVESTIGATE
Trial 1
In Trial 1, students will predict, measure, and draw the forces on a bucket as the bucket is held stationary, and lifted upwards.
a. If necessary, remind students of the steps in the Procedural Tool, Triple Beam Balance Equilibration and Triple Beam Balance Use and Operation.
b. If necessary, remind students of the steps in the Procedural Tool, Spring Scale Use and Operation.
c. Use the steps in the Student Data Record to guide students in setting up the first Trial.
d. Remind students of the method of drawing forces using arrows to represent the direction and magnitude of the forces. Students may record their results in Problem 1a through 1f in their Student Data Records.
Trial 2
In Trial 2, students will predict, measure, and draw the forces on a bucket as it starts to move downwards.
a. Use the steps in the Scientist Data Record to guide students in setting up the second trial.
b. Remind students of the method of drawing forces using arrows to represent the direction and magnitude of the forces. Students should record their results in Problem 2a through 2c of the Student Data Record.
Trial 3
In Trial 3, students will predict, measure, and draw the forces on a bucket, as the bucket moves upwards at a constant speed.
a. Use the steps in the Student Data Record to guide students in setting up the third trial.
b. Remind students of the method of drawing forces using arrows to represent the direction and magnitude of the forces. Students should record their results in Problem 3a through 3c of the Student Data Record.
Trial 4
In Trial 4, students will predict, measure, and draw the forces on a bucket, as the bucket moves downwards at a constant speed.
a. Use the steps in the Student Data Record to guide students in setting up the fourth trial.
b. Remind students of the method of drawing forces using arrows to represent the direction and magnitude of the forces. Students should record their results in Problem 4a through 4c of the Student Data Record.
Trial 5
In Trial 5, students will predict, measure, and draw forces on a bucket, as the bucket slows down while moving upwards.
a. Use the steps in the Student Data Record to guide students in setting up the fifth Trial.
b. Remind students of the method of drawing forces using arrows to represent the direction and magnitude of the forces. Students should record their results in Problem 5a through 5c of the Student Data Record.
Trial 6
In Trial 6, students will predict, measure, and draw forces on a bucket as it slows down while moving downwards.
a. Use the steps in the Student Data Record to guide students in setting up the sixth trial.
b. Remind students of the method of drawing forces using arrows to represent the direction and magnitude of the forces. Students should record their results in Problem 6a through 6c of the Student Data Record.
Note to Teacher: If time in the lab is limited, this Investigation may be suspended after Trial Six. The Investigation may be continued during a further class period.
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Trial 7
In Trial 7, students will predict and measure the forces on a woodblock, resting still on a sandpaper surface, but being pulled by a spring scale. In doing so, students will measure a force that is less than the force of friction. Students have previously learned that a force greater than the force of friction would cause an object to accelerate.
a. Use the steps in the Student Data Record to assist students in setting up the trial.
b. If necessary, remind students of the steps in the Procedural Tools, Triple Beam Balance Equilibration and Triple Beam Balance Use and Operation.
c. If necessary, remind students of the steps in the Procedural Tool, Spring Scale Use and Operation.
d. Students should record their data in Problem 7b through 7i in the Student Data Record.
Trial 8
In Trial 8, students will predict and measure the forces on a woodblock sitting on a sandpaper surface. The woodblock starts to move due to the pull force exerted by a spring scale.
a. Use the steps in the Student Data Record to assist students in setting up the Trial.
b. Students should record their prediction in Problem 8a and their data in Problem 8b in the Student Data Record.
Trial 9
In Trial 9, students will predict and measure the forces on a woodblock on a sandpaper surface. The woodblock is moving at a constant speed due to the pull force exerted by a spring scale.
a. Use the steps in the Student Data Record to assist students in setting up the trial.
b. Students should record their prediction in Problem 9a and their data in Problem 9b in the Student Data Record.
Trial 10
In Trial 10, students will predict and measure the forces on a woodblock on a sandpaper surface. The woodblock is being pulled by a spring scale, but the woodblock starts to slow down due to a decrease in pull force and the maintenance of frictional force.
a. Use the steps in the Student Data Record to assist students in setting up the trial.
b. Students should record their prediction in Problem 10a and their data in Problem 10b in the Student Data Record.
KEYS
CLEAN UP
Let students know your expectations for clean-up. Ask them to clean up.