FarleyPhysics.com

Mass is the quantity of matter, or a measure of something’s inertia.

Weight is the force of gravity on an object.  Gravity can change, mass cannot.

Some videos: ISS Weightlessness, Water Balloons, Walking on Moon, 30 teachers and 3000 ping pong balls,

The Units of mass and weight are different.   kg is the unit of mass and Newton is the unit of weight.

Calculating weight given the mass,  calculating mass given weight, and calculating the acceleration of gravity given mass and weight. using w = mg

For all the questions below, use g = 10 m/s/s.  g on the moon is 1/6 what it is on the Earth.

1.  A ball has a mass of 1 kilogram.  Find its weight in newtons.

2. A bag of groceries has a weight of 44 newtons.  Find its approximate mass in kilograms.

3.  A marble has a mass of  0.002 kilograms.  Find its weight in Newtons.

4.  If an object has a mass of 36 kg, find its mass on the moon and find its weight on the moon.

5.  An astronaut has a mass of 90 kg.  Find his mass and his weight if he is in a flight simulator where the gravitational attraction has been reduced to 1/10 of the earth’s pull.

6.  An object has a mass of 5.5 kilograms.  Find its weight in newtons.

7.  A bag of apples has a weight of 22 newtons.  Find its approximate mass in kilograms.

8.  A paper clip has a mass of  0.001 kilograms.  Find its approximate weight  in newtons.

9.  If an object has a mass of 24 kg, find its mass on the moon and find its weight on the moon.

10. An astronaut has a mass of 85 kg.  Find his mass and his weight if he is in a flight simulator where the gravitational attraction has been reduced to 1/10 of the earth’s pull.

11. Find your weight on Mars, Jupiter, Pluto, and a Neutron Star by using this website.

Page 21 in your notes

1. Newton’s Third Law videos:

Cannon Recoil, gun recoil, Shuttle Launch,

2. Newton’s Third Law Notes

For every action, there is an equal but opposite reaction.

forces come in pairs called action/reaction pairs.  If you apply a force to something, it applies an equal force back at you.

3. Go to the site linked here on Newton’s Third Law.  Read the page and try the Check your Understanding questions.  Draw each situation and summarize the questions and answers in your notes.

4. Do the same thing for Action/Reaction Pairs linked here.

If you have time, Play the lunar lander simulation.

Page 20 in your notes.

Forces and Force diagrams

Go here to learn about forces.  Answer the questions below in your notes.  Be sure to include the question.

1. What is a force?

2. What is a contact force?

3. What is an Action at a distance force?

4. List some Contact forces and some action at a distance forces.

5. What is a Newton?

6. Is force a vector or scalar quantity?  Why?

7. Draw a picture of an object with balanced forces on it.

8. Draw a picture of an object with unbalanced forces on it.

9. What is the gravitational force also known as?

10. What is a “Normal Force”?

11. What is a “Tension Force”?

12. What is a Free-Body Diagram?  Draw one.

13. Draw five free body diagrams from the list given on this page.  Attempt the diagram yourself, then copy the right diagram.  You should have two diagrams for each situation.  Yours and theirs.  Be sure to label all the forces.

14. Answer the two questions here in your notes and be sure to draw the free-body diagram and describe the situation.