GET FOCUSED

• Students will experience the force of gravity for different objects by holding them. Students will then represent the force of gravity by drawing arrows on diagrams to indicate the direction and relative size of the force.
• As students perform their lab experiments, they should keep the following questions in mind:

Can the force of gravity be changed?

Can the force of gravity be measured?

INVESTIGATE

Trial 1

In Trial 1, students will experience the force of gravity for different objects by holding them. Students will then represent the force of gravity by drawing arrows on diagrams to indicate the direction and relative size of the force. This Trial is designed to help students begin to answer the following questions:

• Can the force of gravity be changed?

• Can the force of gravity be measured?

a. Students may complete Trial 1 by following the directions in their Student Data Record. If necessary, to begin the Trial, demonstrate to students how to hold the bucket at arm’s length and how to hold it stationary.

b. Ensure that for each student group, students are assisting the student holding the bucket by removing and adding weights for him or her.

c. Allow students to change roles so that all students have the opportunity to hold the bucket in each condition.

d. Allow students time to complete their answers in Problem 3a through 3e.

Trial 2

In this Trial, students will again hold the bucket stationary in the air. In order to obtain a quantitative measure of the force of gravity acting on the bucket (and hence the weight of the bucket), students will first use a triple beam balance to measure the mass of the bucket and associated objects. Then students will insert a spring scale into the hole in the handle of the white bucket and hang the bucket from the spring scale. Students will record their answers in Problem 4 in their Student Data Records. As students conduct this Trial, they should think about the following questions:

• Can the force of gravity be changed?

• Can the force of gravity be measured?

a. If necessary, remind students of the steps in the Procedural Tools, Triple Beam Balance Equilibration, and Triple Beam Balance Use and Operation.

b. Students will use the Triple Beam Balance to obtain the mass of the bucket and subsequently, the mass of the bucket when objects are added to it. Students should record the mass of the objects in the table.

c. If necessary, assist students in using the calculators to obtain the mass of each object in kilograms.

d. Students should complete the first two columns of the Table prior to using the spring scale.

e. If necessary, remind students of the steps in the Procedural Toolbox, Spring Scale Use, and Operation. Ensure that each student group adjusts the nut at the top of the spring scale in order to equilibrate it prior to use.

f. Demonstrate how to hook the spring scale through the handle of the white bucket.

g. Students should record their data in the Table.

KEYS

CLEAN UP

Let students know your expectations for clean-up. Ask them to clean up.