Qualitative practice with systems

For the following situations, determine whether the energy of the given system is the same at the initial and final states indicated (i.e., is the energy of the system constant or not).

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A block is hung from a spring that is vertical and connected to the ceiling. The block is made to oscillate vertically. Call the initial state when the block is at its highest position and the final state when the block is at its equilibrium position.
Energy of the system is constant Energy of the system is not constant  System: block
Energy of the system is constant Energy of the system is not constant  System: block + ceiling (+ spring) + Earth
Energy of the system is constant Energy of the system is not constant  System: block + Earth

A block on a table (friction between the table and the block is not negligible) is attached to a wall via a spring that is horizontal. You give the block a brief push so that the block travels horizontally. Call the initial state when the spring first reaches its maximum stretch in the initial direction of motion. The final state is when the spring first reaches its zero stretch length.
Energy of the system is constant Energy of the system is not constant  System: block + wall (+ spring) + table
Energy of the system is constant Energy of the system is not constant  System: block + wall (+ spring)
Energy of the system is constant Energy of the system is not constant  System: block + table
Energy of the system is constant Energy of the system is not constant  System: table
Energy of the system is constant Energy of the system is not constant  System: block

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A person wearing roller skates is standing in front of a wall. Assume that the wheels on the skates are good enough that they roll ideally. The person pushes off the wall and begins traveling away from the wall. Call the initial state when the person was standing at rest in front of the wall with her hand touching the wall. The final state is when she has traveled 2 m away from the wall and is moving at a constant speed of 0.69 m/s.
Energy of the system is constant Energy of the system is not constant  System: girl+wall
Energy of the system is constant Energy of the system is not constant  System: wall
Energy of the system is constant Energy of the system is not constant  System: girl

A person is jumping on a trampoline. After coming off of the trampoline, he is in the air for 1.4 seconds. Call the initial state when the trampoline is at its lowest point with the person still on the trampoline. The final state is 0.8 seconds after the person comes off the trampoline.
Energy of the system is constant Energy of the system is not constant  System: girl + Earth
Energy of the system is constant Energy of the system is not constant  System: trampoline
Energy of the system is constant Energy of the system is not constant  System: girl
Energy of the system is constant Energy of the system is not constant  System: girl + trampoline
Energy of the system is constant Energy of the system is not constant  System: girl + trampoline + Earth

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You push a box up a ramp (friction between the box and the ramp is not negligible). Call the initial state when you begin to push the box. Call the final state after you have pushed the box up the ramp a distance of 0.5 m and it is moving with a speed of 2 m/s
Energy of the system is constant Energy of the system is not constant  System: you
Energy of the system is constant Energy of the system is not constant  System: box + ramp + Earth + you
Energy of the system is constant Energy of the system is not constant  System: box + ramp
Energy of the system is constant Energy of the system is not constant  System: box + ramp + Earth
Energy of the system is constant Energy of the system is not constant  System: box

Two cars are driving down the road. They notice that they are going to crash, so both drivers slam on the brakes. The cars skid, but still collide. The cars stick together and eventually slide to a stop. Call the initial state just before the drivers apply the brakes and the final state just after the collision had occurred. Treat this situation as realistically as possible.
Energy of the system is constant Energy of the system is not constant  System: the first car
Energy of the system is constant Energy of the system is not constant  System: both cars
Energy of the system is constant Energy of the system is not constant  System: the second car
Energy of the system is constant Energy of the system is not constant  System: both cars + the ground

Question 1: Electrostatics

a. Draw the electric field lines around a system that consists of two equal positive charges

b. Calculate the electric force that exists between two objects that are 7.3 x 10^-2 m apart and carry charges of 4.5 x 10^-6 C and -7.2 x 10^-6 C. Is this force attractive or repulsive?

c. Write two or three sentences to explain the effect on the electric force between two charged objects if the amount of charge on one of the objects is doubled at the same time as the distance between the objects is doubled.

A 3.61 kg particle has the xy coordinates (-1.06 m, 0.516 m), and a 3.39 kg particle has the xy coordinates (0.820 m, -0.0640 m). Both lie on a horizontal plane. At what (a) x and (b) y coordinates must you place a 2.60 kg particle such that the center of mass of the three-particle system has the coordinates (-0.672 m, -0.106 m)?

Q4. Tiger Woods is known for having one of the fastest driving swings in Golf (among other things). In fact, his Tee-off ball speed was recorded to be 122 MPH.

1. Determine what Tiger Wood’s angular velocity and acceleration are for the club. He is 1.85 meters tall. (Refer to the Anthropometry slides to estimate his shoulder height)

Shoulder height = 1.5133

122 MPH = 54.54 m/s

• A charge of +1.00 millicoulomb is evenly sprayed over the surface of an insulating sphere of radius 10 cm whose center is at position -1.00 m i . A point charge of

+1.00 millicoulomb is at position +1.00 m i . A point charge of -1.00 millicoulomb

is at the origin. What is the ratio of the magnitude of the electrostatic force due to the conducting sphere on the negative charge to the magnitude of the electric force due to

the positive point charge on the negative charge?

• What is the resultant electrostatic force on the negative point charge in (1)?
• What is the resultant electrostatic force on the positive point charge in (1)?
• What is the electric field at the center of the sphere in (1)?

The index of refraction for a certain type of glass is 1.645 for blue light and 1.607 for red light. When a beam of white light (one that contains all colors) enters from air a plate of this glass at an incidence angle of 40.05

1. Explain in two to three paragraphs the physics behind center of mass (or center of gravity) and static equilibrium. Type this up in your own words and supply an equations or pictures that might be useful to your explanations. (Remember to site your source if you use a picture you found on the internet.) (25 points)

A tuning fork generates sound waves with a frequency of 230 Hz. The waves travel in opposite directions along a hallway, are reflected by walls, and return. The hallway is46.0 m long and the tuning fork is located 14.0 m from one end. What is the phase difference between the reflected waves when they meet at the tuning fork? The speed of sound in air is 343 m/s. (Ans in degrees)

Why did Copernicus and Kepler advocate the new heliocentric theory?

A cookie jar is moving up a 25° incline. At a point 55 cm from the bottom of the incline (measured along the incline), the jar has a speed of 1.4 m/s. The coefficient of kinetic friction between jar and incline is 0.12.

(a) How much farther up the incline will the jar move? m

(b) How fast will it be going when it has slid back to the bottom of the incline? m/s

(c) Do the answers to (a) and (b) increase, decrease, or remain the same if we decrease the coefficient of kinetic friction (but do not change the given speed or location)?

decrease, increase, remain the same

5. A car weighs 2200 lbs. Its mass is

a. 2.2 kg
b. 2200 kg
c. 9.8 kg
d. 1000 kg

6. The weight of an object

a. is related to the quantity of matter it contains
b. is essentially the same as its mass but expressed in different units
c. is the force with which it is attracted to the Earth
d. remains unchanged as the height varies

7. The action and reaction forces referred to in the third law of motion

a. are equal in strength and act in the same direction
b. are equal in strength but act in opposite directions
c. act upon the same body
d. always act at right angles to each other

8. Which of the following is a vector quantity

a. time
b. speed
c. mass
d. velocity

9. Which of the following units could be associated with a vector quantity

a. kg
b. seconds
c. cubic m (m³)
d. N

10. An astronaut whose mass is 80 kg on the Earth is in a spacecraft at an altitude of 10 Earth radii above the Earth's surface. His mass there is

a. 8 kg
b. 80 kg
c. 100 kg
d. 40 kg

11. A 2400-kg car whose speed is 6 m/s, rounds a turn whose radius is 60 m. The centripetal force on the car is

a. 1440 N
b. 240 N
c. 147 N
d. 48 N

12. A moving object must have

a. potential energy
b. acceleration
c. kinetic energy
d. all of the above

13. The work done in holding a 100-kg object at a height of 4 m above the floor for 20 s is

a. 0 J
b. 500 J
c. 1000 J
d. 98,000 J

14. A temperature of 98.6°F is the same as a temperature of

a. 98.6°C
b. 37°C
c. 100°C
d. 0°C

15. A 20-kg boy runs up a flight of stairs 4 m high in 4 s. His power output is

a. 80 W
b. 196 W
c. 320 W
d. 784 W

(Note: m/s² is unit of accelaration "meter per second squared")

A 66.5-kg person throws a 0.0500-kg snowball forward with a ground speed of 33.5 m/s. A second person, with a mass of 57.5 kg, catches the snowball. Both people are on skates. The first person is initially moving forward with a speed of 2.35 m/s, and the second person is initially at rest. What are the velocities of the two people after the snowball is exchanged? Disregard the friction between the skates and the ice. (Take the direction the snowball is thrown to be the positive direction. Indicate the direction with the sign of your answer.)thrower     
Your response differs significantly from the correct answer. Rework your solution from the beginning and check each step carefully. m/s (Give your answer to at least three decimal places.)catcher     
Your response differs significantly from the correct answer. Rework your solution from the beginning and check each step carefully.

A person jumps upward off a diving board at 6.0 m/s and hits the water 2.0 seconds later (including the up and down time). About how fast will she be going just before she hits the water?

The three principal rays for converging (concave) mirrors: 1. Any incident ray parallel to the principal axis is reflected through the focal point (which is located at ½ R where R is the distance from the mirrors center (or vertex) to the center of curvature C. 2. Any incident ray which passes through the focal point is reflected parallel to the principal axis. 3. Any incident ray which passes through the mirror’s center of curvature C (i.e. along the radius) is reflected back upon itself. The three principal rays for diverging (convex) mirrors: 1. Any incident ray parallel to the principal axis is reflected as if it came from the focal point (which is located at ½ R behind the mirror’s surface where R is the distance from the mirror’s center (or vertex) to the center of curvature C. 2. Any incident ray which is directed towards the focal point is reflected parallel to the principal axis. 3. Any incident ray directed towards the mirror’s center of curvature C (i.e. along the radius) is reflected back upon itself. Drawing ray diagrams:

Finish the ray diagrams (Show your work) for the following concave and convex mirror setups using the rules for diagramming as given above. Do this for

a) an object located between C and F

b) an object located beyond C

c) an object located between V and F

It is a calm summer day in southeast Iowa at the Ottumwa air traffic control radar installation - except there are some small, locally intense thunderstorms passing through the general area. Only two planes are in the vicinity of the station: American Flight 1003 is traveling from Minneapolis to New Orleans is approaching from the north-northwest, and United Flight 336 is traveling from Los Angeles to New York is approaching from west-southwest. Both are on the path that will take them directly over the radar tower. There is plenty of time for the controllers to adjust the flight paths to insure a safe separation of the aircraft.

Suddenly lightning strikes a power substation five miles away, knocking out the power to the ATC installation. There is, of course, a gasoline powered auxiliary generator, but it fails to start. In desperation, a mechanic rushes outside and kicks the generator; it sputters to life. As the radar screen flickers on, the controllers find that both flights are at 33,000 feet. The American flight is 32 nautical miles (horizontally) from the tower and is approaching it on a heading of 171 degrees at a rate of 405 knots. The United flight is 44 nautical miles from the tower and is approaching it on a heading of 81 degrees at a rate of 465 knots.

a. At the instant of this observation, how fast is the distance between the planes decreasing?
b. How close will the planes come to each other?
c. Will they violate the FAA's minimum separation requirement of 5 nautical miles?
d. How many minutes do the controllers have before the time of closest approach?
e. Should the controllers run away from the tower as fast as possible?

The specific questions asked above are a guide to your work and suggestions of the directions to pursue. Your report must contain not just answers to questions but explanations as well.