Read Worksheet over Unit 4 Reading, "An Introduction to Forces and Newton's Laws" text version

Worksheet #1 over Unit 6 Reading, "An Introduction to Forces and Newton's Laws" Aristotle's (Greek philosopher and scientist, 384-322 BC) ideas of motion were much different than Galileo. 1. Aristotle believed that all objects were made up of four elements. What were these four elements?

2. According to Aristotle why would smoke rise?

3. A rock thrown upward falls back to the Earth? Why would it fall back to the Earth according to Aristotle? What explanation would Galileo offer?

4. According to Aristotle, what do you need to keep doing to an object to keep it moving?

5. Aristotle discussed the "Prime Mover." Who or what was the Prime Mover?

6. What important idea did Galileo make with his telescopic observations?

7. Galileo came up with his concept of inertia. What is inertia?

8. What did Isaac Newton do with Galileo's ideas of motion?

Worksheet #1 over Unit 6 Reading, "An Introduction to Forces and Newton's Laws"

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9. Newton takes Galileo's concept of inertia and it becomes his first Law of Motion. It says that objects in motion will remain in motion unless a force acts to change this motion. Many moving objects eventually stop moving. What makes the moving block (discussed in the reading) stop moving?

10. In the reading, friction is called a `hidden force.' Why is friction called a hidden force?

11. What would happen to the moving block if we decrease the friction (with oil or lubrication)?

12. Consequently, what would the moving block do if we could remove friction entirely (not really possible to do)?

13. Compare Aristotle and Galileo in terms of this question: If we remove friction, what would we see happen to the moving block?

14. In class, we discussed seat belts. Why are seat belts a good example of Newton's First Law of Motion?

Worksheet #1 over Unit 6 Reading, "An Introduction to Forces and Newton's Laws"

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Worksheet #2, Unit 6, Reading, "Mass vs. Weight" 1. Mass and weight (W or Fg) can be confusing. Define each. 2. How could you change your mass?

3. What would be the correct unit for a mass? What about for Weight?

4. How do you calculate weight if you know the mass?

5. Why would your weight change on Mars but not your mass?

6. Why is it said that weight is an "attractive" force?

7. Is there a correlation between weight and volume? For example do "big" objects weigh more?

8. Should a weight lifter be really called a "mass-lifter"?

9. Your car has a large mass. If you drove it around the moon where it has a smaller weight, would it be easier to move horizontally?

10. Where could you go where you would have a weight of zero? Would your mass be zero, too?

Worksheet #2, Unit 6, Reading, "Mass vs. Weight" p. 1 9/23/2009

W (or Fg) = mg, where m = mass in kilograms and g = the acceleration due to gravity (this is 9.8 m/s^2 on the Earth).

* Use "g" = 9.8 m/s2 as the acceleration of gravity upon the Earth's surface * A force is a push or pull, measured in Newtons. One lb of force (force units in the USA) = 4.45 N. * 1st Law: "Every object continues in a state of rest, or of motion in a straight line at constant speed, unless it is compelled to change that state by forces exerted on it."

1. Going for a school record, Cameron, the weightlifter, can lift a 230 kg barbell. a) What is the weight of the barbell on the earth? (answer = 2254 N) b) What is the weight of the barbell in pounds? (answer = 506.5 lbs)

2. Ryan weighs 45 lbs on the Earth. a) How many Newtons does he weigh? (answer = 200.25 N) b) How many kilograms does he mass? (answer = 20.4 kg) c) If the "g" on Neptune is 12 m/s2, what would he weigh there? (answer = 244.8 N)

3. On the moon, the gravity is 1/6 that of the Earth's. Buzz Aldrin, who along with Neil Armstrong, were the first two individuals to walk on the moon's surface. While on the moon, Buzz had to carry around his life support system which weighed 1760 N on the Earth. a) What did this life support system weigh on the moon? (answer = 293.3 N) b) How many kilograms did it mass? (answer = 179.6 kg) c) What did it weigh on the Earth in pounds? (answer = 395.5 lbs) d) What did it weigh on the moon in pounds? (answer = 65.9 lbs)

Worksheet #2, Unit 6, Reading, "Mass vs. Weight"

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Unit 6, Worksheet #3, The Normal Force

1. A book lying flat on a table experiences a normal force. There are two forces vectors present, the normal force and the weight vector. Draw both of these forces.

2. Now you come up to the book and push down a bit. You have just added a third force, Fpush or Fapplied. Draw the forces now. How does the magnitude of the normal force change?

3. In the picture in the reading, the normal force is drawn on the thin piece of wood or plastic. Note: The Weight vector is not draw on this picture. We see the thin piece of wood deform. What causes this deformation?

4. If we add enough weight to the thin piece of wood it will break. What happens to the normal force now?

5. The block drops and eventually falls to the floor and comes to rest. Is there a normal force that exists now?

Draw the weight vector and normal force now.

Unit 6, Worksheet #3, The Normal Force

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6. We see that the thin piece of wood deforms and bends. But what about the book on the desk? Does the desk deform? Please explain...

7. To name a force `normal' seems kinda strange. Why are these forces called `normal' Is it the case that they are not abnormal? Hint...you may need to look up the mathematical definition for `normal'.

8. The normal force is just one example of a support force. Explain...

9. You take a wagon and pull you kid brother. You pull it two different ways:

Explain how the normal force would be different in both cases.

10. Normal forces are a bit more difficult on incline planes. If we move the box from a flat, horizontal surface to the incline plane, we still have a normal force but now the direction is much different. Explain...

Can you understand now why the normal force is called `normal'? Explain. Now the normal force does not equal the weight of the box. It equals mg(cos)...This is definitely something we should talk about.

Unit 6, Worksheet #3, The Normal Force

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Worksheet #4 Free Body or Force diagrams...

Drawing Free-Body Diagrams Free-body diagrams are diagrams used to show the relative magnitude and direction of all forces acting upon an object in a given situation. A free-body diagram is a special example of the vector diagrams; these diagrams will be used throughout your study of physics. The size of the arrow in a free-body diagram is reflective of the magnitude of the force. The direction of the arrow reveals the direction in which the force acts. Each force arrow in the diagram is labeled to indicate the type of force. It is customary in a free-body diagram to represent the object by a box or a small circle and to draw the force arrow from the center of the box or circle outward in the direction in which the force is acting. One example of a free-body diagram is shown to the right. The free-body diagram above depicts four forces acting upon the object. Objects do not always have four forces acting upon them. There will be cases in which the number of forces depicted by a freebody diagram will be one, two, or three. There is no hard and fast rule about the number of forces which must be drawn in a free-body diagram. The only rule for drawing free-body diagrams is to depict all the forces which exist for that object in the given situation. Thus, to construct free-body diagrams, it is extremely important to know the types of forces. If given a description of a physical situation, begin by using your understanding of the force types to identify which forces are present. Then determine the direction in which each force is acting. Finally, draw a box and add arrows for each existing force in the appropriate direction; label each force arrow according to its type. Apply the method described in the reading to construct free-body diagrams for the situations described below. Use the symbols we discussed in class. Draw force vectors on the circle and label them. 1. A book is at rest on a table top. Diagram the forces acting on the book.

2. A girl is suspended motionless from the ceiling by a rope. Diagram the forces acting on the girl as she holds onto the rope.

3. An egg is free-falling from a nest in a tree. Neglect air resistance. Diagram the forces acting on the egg as it falls.

4. An egg is falling (not freely, do not neglect air resistance) from a nest in a tree. Diagram the forces acting on the egg as it falls.

5. A rightward force is applied to a book in order to move it across a desk with a rightward acceleration. Consider frictional forces. Neglect air resistance. Diagram the forces acting on the book.

6. A rightward force is applied to a book in order to move it across a desk at constant velocity. Consider frictional forces. Neglect air resistance. Diagram the forces acting on the book.

7. A car is stopped at a stop light.

8. A skydiver is descending with a constant velocity. Consider air resistance. Diagram the forces acting upon the skydiver.

9. A car is parked on a sloped street.

10. A hot air balloon is accelerating upward.

11. A car is coasting to the right and slowing down. Diagram the forces acting upon the car.

Name Date Pd

Worksheet 5, More Drawing Force Diagrams

In each of the following situations, represent the object with a dot. Draw and label all the forces using standard force symbols as learned in class.

1. Object lies motionless on a surface. 2. Object slides at constant speed along a Smooth (frictionless) surface.

3. Object slows due to friction (rough surface).

4. Object slides on a smooth incline.

5. Friction on an incline prevents sliding.

6. An object is suspended from the ceiling.

7. An object is suspended from the ceiling.

8. The object is motionless.

9. The object is motionless.

10. The object is motionless.

Worksheet, Drawing Force Diagrams

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11. The object is pulled by a force parallel to the surface. The surface is rough or has friction.

12. The object is pulled by a force at an angle to the surface. The surface is rough.

13. The object is pulled upward at constant speed.

13. A hot air balloon is held down to keep it From accelerating upward.

15. The object is falling (no air resistance).

16. The object is falling at constant (terminal) velocity.

17. The ball is rising in a parabolic trajectory. Do not neglect air resistance

18. A rocket is accelerating straight upward.

19. A skier is accelerating down a slope. There is friction and air resistance.

20.A big block of mass M is attached via a string to a smaller block of mass m. A student attaches a string to block M and pulls everything to the right along the rough surface. Both blocks travel at constant velocity. Do force diagrams for each block separately.

Worksheet, Drawing Force Diagrams

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Worksheet #6 over Unit 6 reading: Determining the Net Force 1. When we draw forces on objects and the forces act along an axis, the forces can be summed collinearly (forces up and right are considered positive; forces down and left are considered negative).

When all the forces sum up = 0, then we say the object is in equilibrium. In one case of equilibrium the object is stationary. All the forces are balanced. Let's say that the above box has a mass of 10 kg. Label the two forces acting on the box with the correct amount of force for each one. However, there is another case of equilibrium: the object could be moving but at a constant velocity (not accelerating: i.e. not getting faster or slower). This is also equilibrium.

In this case, let's say you push the 10 kg box to the right with a force of 200 N. The box moves at constant velocity. Friction acts to oppose your push equally. Label all of your forces and put correct amounts of forces for each one. What happens if the friction is smaller than your push force? Let's say that friction acts at 100 N instead of 200 N. What is the net force now acting horizontally? How about vertically?

This situation is now called an unbalanced (non-equilibrium) situation. Forces balance in the y direction but not the x direction. How will the object move now?

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Worksheet #4 over Unit 6 reading: Determining the Net Force

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Let's say that you push the object but then release your push so you are not touching it now. The friction on the 10 kg box is still 50 N.

Draw the forces present and label them. Make sure to put correct amounts. Is the box in equilibrium now? How do you know? What is the ensuing type of motion?

Let's say we have a rocket:

If the rocket has a mass of 1000 kg, what is the upward force (thrust) if the rocket moves at a constant velocity? Draw the force vectors on the rocket (ignore air resistance). Would this be an equilibrium or non-equilibrium situation?

However, the rocket loses mass over time. However, the thrust stays somewhat constant over time. What happens now to the weight vector? What happens to the thrust vector? Would this be an equilibrium or non-equilibrium situation? What type of motion would the rocket now have?

Worksheet #4 over Unit 6 reading: Determining the Net Force

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General Physics, Unit 6 Worksheet 7: Preparation for the quiz

1. Compare and contrast contact vs field forces. Give examples of each.

2. How do we calculate the weight of an object?

3. What is the weight of a 40 kg object?

4. What would be the weight of the 40 kg object on the moon?

5. What changes depending on location in the universe, mass or weight? Explain.

6. What is Newton's First Law?

7. Galileo used a term called INERTIA. What is inertia?

8. Make sure you know symbols for common forces.

9. Why is a tensional or a normal force called a support force?

10. How are tensional forces created?

11. In what direction is the weight vector always drawn?

12. What is the normal force?

13. In what direction is the normal force drawn?

14. Express Newton's second law in symbol form.

15. Why do we write Fnet = ma and not F=ma?

16. In terms of forces, what does it mean for an object to be in `equilibrium?'

17. What type(s) of motion does an object in equilibrium have?

18. How does that motion change for the object if the forces on the object are unbalanced?

19. One common way of phrasing Newton's third law is action-reaction. What is meant by this?

20. Is gravity considered a contact or a field force? Explain.

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Worksheet over Unit 4 Reading, "An Introduction to Forces and Newton's Laws"

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