Part 1: Relationship Between Mass and Weight

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UNIT 2.3 WS 4 – Calculating Forces

Part 1: Relationship between mass and weight

1. An object has a mass of 8.00 kg. What is the gravitational force on the object by the earth?

2. The earth exerts a gravitational force of 0.500 N on an object. What is the mass of the object in grams?

3. On a voyage to distant planets, you determine the gravitational field strength by measuring weights on a scale and masses on an inertial balance. You have with you the following masses. Some have the original mass marked on them, while others are actually marked with the weight. You, being a well-trained astronaut, know that Earth’s gravitational field strength is 10 N/kg.

Use the information given above to fill in the missing information regarding the weight and mass of the object on Algon (below).

4. A 5kg mass is hung from a spring scale. Recall that spring scales measure FORCES in Newtons!

a. What will the scale read when it and the mass are held motionless? ______

b. Will the scale reading be different if it and the mass are moving upward at constant speed? Explain briefly.

c. Will the scale reading be different if it and the mass are accelerating upward? Explain briefly.

Part 2: Calculating Forces

5. One of your classmates, in a fit of unrestrained ego, jumps onto a lab table:

a) Draw a qualitative force diagram for the table. Use marks on the vectors to show the balance of forces.

b) Your classmate’s mass is 65 kg and the table weighs 500 N. Calculate the upward force on the table by the floor. Show your work!

c) Find the mass of the table.

6. The gravitational field strength on the moon is 1.63 N/kg. If a rock on the moon weighs 2000N, how much does the same rock weigh on the earth?

7. Challenge: The person is pulling up on the spring scale, but the box remains on the table. Find the values of each of the following. (A force diagram with arrows representing all forces acting on the block is strongly recommended.)

a.) Force of the table on the box. ______

b.) Force of the box on the table. ______

c.) Force of gravity acting on the box. ______

d.) Force of the hand on the spring scale. ______

e.) Force of the box on the spring scale. ______