Physics Name ______
Newton’s Second Law Period _____
Use the following site to answer the questions below.
http://www.glenbrook.k12.il.us/gbssci/phys/Class/newtlaws/newtltoc.html
HTTP://WWW.GLENBROOK.K12.IL.US/GBSSCI/PHYS/CLASS/NEWTLAWS/NEWTLTOC.HTML
Lesson Three
1. Newton’s Second Law States
The ______of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object.
2. Newton’s Second Law in a formula is
______
3. The units for F are (give an equation showing the unit and what it is equivalent to.)
______
4. Complete the table below
Force in newtons / Mass in kilograms / Acceleration in m/s/s10 / 2
20 / 2
20 / 4
2 / 5
10 / 10
5. Consider the two ticker tape traces below for an acceleration of a car. From the trace, determine the direction of the net force which is acting upon the car. Show with an arrow on the diagram the direction of the force.
6. What acceleration will result when a 12-N net force applied to a 3-kg object? A 6-kg object? ______
7. A net force of 16 N causes a mass to accelerate at a rate of 5 m/s2. Determine the mass. ______
8. An object is accelerating at 2 m/s2. If the net force is tripled and the mass is doubled, then what is the new acceleration? ______
9. An object is accelerating at 2 m/s2. If the net force is tripled and the mass is halved, then what is the new acceleration? ______
10. Are You Infected with the Misconception?
Two students are discussing their physics homework prior to class. They are discussing an object which is being acted upon by two individual forces (both in a vertical direction); the free-body diagram for the particular object is shown at the right. During the discussion, Anna Litical suggests to Noah Formula that the object under discussion could be moving. In fact, Anna suggests that if friction and air resistance could be ignored (because of their negligible size), the object could be moving in a horizontal direction. According to Anna, an object experiencing forces as described at the right could be experiencing a horizontal motion as described below.
Noah Formula objects, arguing that the object could not have any horizontal motion if there are only vertical forces acting upon it. Noah claims that the object must be at rest, perhaps on a table or floor. After all, says Noah, an object experiencing a balance of forces will be at rest. Who do you agree with?
______
______
______
11. The process of determining the acceleration of an object demands that the mass and the net force are known. If mass (m) and net force (Fnet) are known, then the acceleration is determined by use of the equation.
______
12. An applied force of 50 N is used to accelerate an object to the right across a frictional surface. The object encounters 10 N of friction. Use the diagram to determine the normal force, the net force, the mass, and the acceleration of the object. (Neglect air resistance.)
13. An applied force of 20 N is used to accelerate an object to the right across a frictional surface. The object encounters 10 N of friction. Use the diagram to determine the normal force, the net force, the coefficient of friction ("mu") between the object and the surface, the mass, and the acceleration of the object. (Neglect air resistance.)
14. A 5-kg object is sliding to the right and encountering a friction force which slows it down. The coefficient of friction ("mu") between the object and the surface is 0.1. Determine the force of gravity, the normal force, the force of friction, the net force, and the acceleration. (Neglect air resistance.)
15. Free-body diagrams for four situations are shown below. The net force is known for each situation. However, the magnitudes of a few of the individual forces are not known. Analyze each situation individually and determine the magnitude of the unknown forces.
16. A rightward force is applied to a 6-kg object to move it across a rough surface at constant velocity. The object encounters 15 N of frictional force. Use the diagram to determine the gravitational force, normal force, net force, and applied force. (Neglect air resistance.)
17. A rightward force is applied to a 10-kg object to move it across a rough surface at constant velocity. The coefficient of friction between the object and the surface is 0.2. Use the diagram to determine the gravitational force, normal force, applied force, frictional force, and net force. (Neglect air resistance.)
18. A rightward force is applied to a 5-kg object to move it across a rough surface with a rightward acceleration of 2 m/s/s. The coefficient of friction between the object and the surface is 0.1. Use the diagram to determine the gravitational force, normal force, applied force, frictional force, and net force. (Neglect air resistance.)
19. A rightward force of 25 N is applied to a 4-kg object to move it across a rough surface with a rightward acceleration of 2.5 m/s/s. Use the diagram to determine the gravitational force, normal force, frictional force, net force, and the coefficient of friction between the object and the surface. (Neglect air resistance.)
20. Go to Free Fall and Air Resistance. Answer the following true or false questions posed in the first animation. This is without air resistance.
a. The elephant and the feather each have the same force of gravity.
b. The elephant has more mass, yet both elephant and feather experience the same force of gravity.
c. The elephant experiences a greater force of gravity, yet both the elephant and the feather have the same mass.
d. On earth, all objects (whether an elephant or a feather) have the same force of gravity.
e. The elephant weighs more than the feather, yet they each have the same mass.
f. The elephant clearly has more mass than the feather, yet they each weigh the same.
g. The elephant clearly has more mass than the feather, yet the amount of gravity (force) is the same for each.
h. The elephant has the greatest acceleration, yet the amount of gravity is the same for each.
21. Answer the following true or false questions posed in the second animation. This is with air resistance.
a. The elephant encounters a smaller force of air resistance than the feather and therefore falls faster.
b. The elephant has a greater acceleration of gravity than the feather and therefore falls faster.
c. Both elephant and feather have the same force of gravity, yet the acceleration of gravity is greatest for the elephant.
d. Both elephant and feather have the same force of gravity, yet the feather experiences a greater air resistance.
e. Each object experiences the same amount of air resistance, yet the elephant experiences the greatest force of gravity.
f. Each object experiences the same amount of air resistance, yet the feather experiences the greatest force of gravity.
g. The feather weighs more than the elephant, and therefore will not accelerate as rapidly as the elephant.
h. Both elephant and feather weigh the same amount, yet the greater mass of the feather leads to a smaller acceleration.
i. The elephant experiences less air resistance and than the feather and thus reaches a larger terminal velocity.
j. The feather experiences more air resistance than the elephant and thus reaches a smaller terminal velocity.
k. The elephant and the feather encounter the same amount of air resistance, yet the elephant has a greater terminal velocity.
22. For each case, use the diagrams to determine the net force and acceleration of the skydiver at each instant in time. Then use the pop-up menus to view the answers.
23. Go to the next animation (after the section on terminal velocity).
a. What is the acceleration of the sky diver when the air resistance equals their weight? ______
b. When the parachute opens, is the upward force ever bigger than the downward force? ______
c. Does the sky diver ever move up? ______
Physics Name ______KEY______
Newton’s Second Law Period _____
Use the following site to answer the questions below.
http://www.glenbrook.k12.il.us/gbssci/phys/Class/newtlaws/newtltoc.html
Lesson Three
1. Newton’s Second Law States
The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object.
2. Newton’s Second Law in a formula is
Fnet = m * a
3. The units for F are (give an equation showing the unit and what it is equivalent to.)
4. Complete the table below
Mass in kilograms / Force in newtons / Acceleration in m/s/s10 / 2
20 / 2
20 / 4
2 / 5
10 / 10
5. Consider the two ticker tape traces below for an acceleration of a car. From the trace, determine the direction of the net force which is acting upon the car. Show with an arrow on the diagram the direction of the force.
6. What acceleration will result when a 12-N net force applied to a 3-kg object? A 6-kg object? ______
7. A net force of 16 N causes a mass to accelerate at a rate of 5 m/s2. Determine the mass. ______
8. An object is accelerating at 2 m/s2. If the net force is tripled and the mass is doubled, then what is the new acceleration? ______
9. An object is accelerating at 2 m/s2. If the net force is tripled and the mass is halved, then what is the new acceleration? ______
10. Are You Infected with the Misconception?
Two students are discussing their physics homework prior to class. They are discussing an object which is being acted upon by two individual forces (both in a vertical direction); the free-body diagram for the particular object is shown at the right. During the discussion, Anna Litical suggests to Noah Formula that the object under discussion could be moving. In fact, Anna suggests that if friction and air resistance could be ignored (because of their negligible size), the object could be moving in a horizontal direction. According to Anna, an object experiencing forces as described at the right could be experiencing a horizontal motion as described below.
Noah Formula objects, arguing that the object could not have any horizontal motion if there are only vertical forces acting upon it. Noah claims that the object must be at rest, perhaps on a table or floor. After all, says Noah, an object experiencing a balance of forces will be at rest. Who do you agree with?
Anna is correct. If the object was in motion to begin with it
will stay in motion.
11. The process of determining the acceleration of an object demands that the mass and the net force are known. If mass (m) and net force (Fnet) are known, then the acceleration is determined by use of the equation.
12. An applied force of 50 N is used to accelerate an object to the right across a frictional surface. The object encounters 10 N of friction. Use the diagram to determine the normal force, the net force, the mass, and the acceleration of the object. (Neglect air resistance.)
13. An applied force of 20 N is used to accelerate an object to the right across a frictional surface. The object encounters 10 N of friction. Use the diagram to determine the normal force, the net force, the coefficient of friction ("mu") between the object and the surface, the mass, and the acceleration of the object. (Neglect air resistance.)
14. A 5-kg object is sliding to the right and encountering a friction force which slows it down. The coefficient of friction ("mu") between the object and the surface is 0.1. Determine the force of gravity, the normal force, the force of friction, the net force, and the acceleration. (Neglect air resistance.)
15. Free-body diagrams for four situations are shown below. The net force is known for each situation. However, the magnitudes of a few of the individual forces are not known. Analyze each situation individually and determine the magnitude of the unknown forces.
16. A rightward force is applied to a 6-kg object to move it across a rough surface at constant velocity. The object encounters 15 N of frictional force. Use the diagram to determine the gravitational force, normal force, net force, and applied force. (Neglect air resistance.)
17. A rightward force is applied to a 10-kg object to move it across a rough surface at constant velocity. The coefficient of friction between the object and the surface is 0.2. Use the diagram to determine the gravitational force, normal force, applied force, frictional force, and net force. (Neglect air resistance.)
18. A rightward force is applied to a 5-kg object to move it across a rough surface with a rightward acceleration of 2 m/s/s. The coefficient of friction between the object and the surface is 0.1. Use the diagram to determine the gravitational force, normal force, applied force, frictional force, and net force. (Neglect air resistance.)