61. Suppose a highly trained athlete consumes oxygen at a rate of 70.0 mL/(min · kg) during a 30.0-min workout. If the athlete’s mass is 78.0 kg and their body functions as a heat engine with a 20.0% efficiency, calculate (a) their metabolic rate in kcal/min and (b) the thermal energy in kcal released during the workout.

Mario, a hockey player, is skating due south at a speed of 6.35 m/s relative to the ice. A teammate passes the puck to him. The puck has a speed of 8.09 m/s and is moving in a direction of 22.0 ° west of south, relative to the ice. What are (a) the magnitude and (b) direction (relative to due south) of the puck's velocity, as observed by Mario?

1. At a certain moment in time, two identical, positively charged particles are flying horizontally toward each other. Let the xx-axis be the axis along which the particles are moving, and let the origin lie directly between both particles. Let the yy-axis be oriented pointing vertically up and the zz-axis point directly out from the origin.
   
   1) Which combination of options below are the best combination of corrections that you might make to your friend's diagram? [Enter your answer as a string of the letter options you believe are correct. For instance, if you think options A, D, and E are correct, then enter "ADE"]
   
   A) The particles exert magnetic forces on each other.
   B) The magnetic fields of each particle reinforce each other at positions equidistant from each of the particles.
   C) The total magnetic field at points vertically above the positive xx-axis point in the positive zz direction.
   D) The total magnetic field at points vertically below the negative xx-axis point in the negative zz direction.
   E) None of the above
2. A circular loop of wire has current flowing through it. You are looking straight down at this loop from above. The flow of the current through the loop relative to you can be either clockwise or counter-clockwise around the loop. The options describe a series of experiments involving either a magnet or another current loop brought down toward the original. The current in the original loop can be changed between experiments. Choose the combination of options below are physically consistent. [Enter your answer as a string of the letter options you believe are correct. For instance, if you think options A, D, and E are correct, then enter "ADE"]
   
   A) A magnet's south pole is repelled as it is brought down to the loop from above. Therefore, the current flows clockwise.
   B) A magnet's north pole is repelled as it is brought down to the loop from above. Therefore, the current flows counter-clockwise.
   C) A counter-clockwise current loop above the original is attracted. Therefore, the current flows clockwise.
   D) A clockwise current loop above the original is repelled. Therefore, the current flows counter-clockwise.
   E) None of the above
3. Two positively charged particles are travelling through space in each others' vicinity. Using the standard xx-yy-zz coordinate grid, particle 1 travels along the positive xx direction while particle 2 travels along the positive yy direction, heading directly for the first particle from below.
   
   Which combination of options below are the most accurate combination of statements. [Enter your answer as a string of the letter options you believe are correct. For instance, if you think options A, D, and E are correct, then enter "ADE"]
   
   A) Particle 1's magnetic field at particle 2's location points in along the zz-axis.
   B) Particle 2 feels a magnetic force pushing down the negative yy direction.
   C) Particle 2's magnetic field at the location of particle 1 is zero.
   D) Particle 1 feels no magnetic force due to particle 2's magnetic field.
   E) None of the above
4. An electric motor is a device that transfers electrically stored energy into kinetic energy. A very crude one would consist of a conducting wire shaped as a loop with a steady electric current passing through it placed in a uniform magnetic field. Let's imagine that the magnetic field is directed along the positive xx-axis, which we'll set up as going from left to right. The yy-axis points up and the zz-axis points out. Assume an absence of any frictional effects.
   
   Which combination of options below are the most accurate combination of statements? [Enter your answer as a string of the letter options you believe are correct. For instance, if you think options A, D, and E are correct, then enter "ADE"]
   
   A) If the current loop's dipole moment is initially aligned with the field, there will be no resulting rotational motion.
   B) Maximum potential energy in this system occurs when the dipole moment points in the −i^−i^ direction
   C) If the dipole moment initially points along the k^k^ direction, it's left end will feel a force pushing up along the j^j^ direction.
   D) If the dipole moment initially points along the k^k^ direction, it's right end will feel a force pushing in along the −k^−k^ direction.
   E) None of the above
5. An electron gun sends out a beam of electrons whose kinetic energies are all about 54 μμeV. (1 μeV=1.6×10−25 J1 μeV=1.6×10−25 J.) You need to set up a magnetic field perpendicular to the beam that causes it to turn through a 90∘∘ circular arc of length 2 mm. How strong must the magnetic field be?
6. You take a wire and wind it into a circular loop (leaving the two ends free so that they can be connected to a power supply). You take a longer wire and wind it around making 6 turns of the same radius as your first single loop. If you run the same amount of current through both wires, compare the magnetic dipole moment magnitudes of the two setups. What is the ratio of the multi-loop current's dipole moment magnitude to that of the single loop current?
7. Two particles, both carrying charge 6 C are traveling parallel to each other with velocities of v⃗ =12000i^v→=12000i^ in m/s. They are positioned at the points (0,2,0)(0,2,0) and (0,−2,0)(0,−2,0). What is the magnitude and direction of the magnetic field at (0,2,0)(0,2,0) due to the particle located at (0,−2,0)(0,−2,0)? [Enter the magnitude in answer box 1 and the direction as one of either "in", "out", "up", "down", "left", or "right" in answer box 2. Assume that the xx-axis corresponds to left/right, the yy-axis corresponds to up/down, and the zz-axis corresponds to in/out.]
8. What is the force exerted by the magnetic field you calculated above on the particle at that location? Compare this to the direction of the electric force on the particle. [Enter the magnitude of the force in the first answer box and its direction in the second. Enter the direction of the electric force on the particle in the third box. For the directions enter either "in", "out", "up", "down", "left", or "right"]
9. How fast would the particles have to travel in order for there to be a balance between the magnetic and electric forces they exert on each other?
10. Geordi La Forge was born blind, but has a VISOR that allows him to perceive a broad range of the electromagnetic spectrum. Let's suppose that there's a setting that allows Geordi to distinguish electric and magnetic fields from one another. The VISOR also gives him readings on voltage differences between various points in space. If Geordi were to walk by a uniform magnetic field that was not moving relative to the ground, what would he see?
    
    Choose the best combination of options below. [Enter your answer as a string of the letter options you believe are correct. For instance, if you think options A, D, and E are correct, then enter "ADE"]
    
    A) Identical magnetic field vectors at every point in space.
    B) There would only be magnetic field vectors since their are no electric field sources.
    C) Non-zero voltage differences along displacements perpendicular to the magnetic field vectors.
    D) Non-zero voltage differences along displacements parallel to the magnetic field vectors.
    E) None of the above
11. A loop of copper (a conducting material) is carried across a region of space with a non-zero uniform magnetic field so that the area surrounded by the loop is perpendicular to the field direction. Imagine the situation is oriented so that the magnetic field is coming out of the screen toward you, and the loop is being pulled toward the right.
    
    Which combination of options below is most accurate? [Enter your answer as a string of the letter options you believe are correct. For instance, if you think options A, D, and E are correct, then enter "ADE"]
    
    A) The magnetic flux through the loop is decreasing.
    B) The induced current flows clockwise.
    C) Nothing would be changed if the field were not uniform.
    D) Turning the loop around would induce a current.
    E) None of the above

The intensity of an earthquake wave passing through the Earth is measured to be 2.5×106 J/m2⋅s at a distance of 49 km from the source.

a) What was its intensity when it passed a point only 2.0 km from the source?

b) At what rate did energy pass through an area of 2.0 m2 at 2.0 km?

A particular car engine operates between temperatures of 400°C (inside the cylinders of the engine) and 20°C (the temperature of the surroundings).
Given these two temperatures, what is the maximum possible efficiency the car can have? (Note that actual car engine efficiencies are in the 20-25% range.)
_______ %

Part (b)

A particular car engine operates between temperatures of 400°C (inside the cylinders of the engine) and 20°C (the temperature of the surroundings).
If the car was somehow able to operate at its maximum efficiency, determine how much heat must be obtained by burning fuel in the car’s engine to accelerate a 1500 kg car from rest to a speed of 100 km/h (neglect resistive forces). Note that a number like 1.23x10^9 can be entered as 1.23e9
_______ J

The water flow rate for a particular sprinkler is 16 gpm. The water must be projected at least 25 feet in radius. The sprinkler is mounted 11 feet above the ground and is aimed at an angle of 29 degrees above the horiztonal. With what velocity must the water leave the sprinkler? What diameter (inches) should the opening be to achieve this velocity?

A 1.8 kg , 20-cm-diameter turntable rotates at 130 rpm on frictionless bearings. Two 510 g blocks fall from above, hit the turntable simultaneously at opposite ends of a diameter, and stick.What is the turntable's angular velocity, in rpm, just after this event?

n ideal gas is enclosed in a cylinder with a movable piston on top of it. The piston has a mass of 8,000 g and an area of 5.00 cm2 and is free to slide up and down, keeping the pressure of the gas constant. (a) How much work is done on the gas as the temperature of 0.180 mol of the gas is raised from 30.0°C to 325°C?

A 1300 kg aircraft going 35 m/s collides with a 1500 kg aircraft that is parked and they stick together after the collision and are going 16.3 m/s after the collision. If they skid for 14.3 seconds before stopping, how far did they skid? Hint: Are the aircraft moving at a constant velocity after the collision or do they experience an acceleration?

During a relay race, you run the first leg of the race, a distance of 1.8 ✕ 102 m to the north, in 22.34 s. You then run the same distance back to the south in 24.20 s in the second leg of the race. Suppose the positive y axis points to the north. (Express your answers in vector form). (a) What is your average velocity for the first leg of the relay race? vav, y = Incorrect: Your answer is incorrect. m/s (b) What is your average velocity for the entire race? vav, y = Correct: Your answer is correct. m/s

A flywheel turns through 30 rev as it slows from an angular speed of 5.5 rad/s to a stop. (a) Assuming a constant angular acceleration, find the time for it to come to rest. (b) What is its angular acceleration? (c) How much time is required for it to complete the first 15 of the 30 revolutions?

You stand on a straight desert road at night and observe a vehicle approaching. This vehicle is equipped with two small headlights that are 0.621m apart. At what distance, in kilometers, are you marginally able to discern that there are two headlights rather than a single light source? Take the wavelength of the light to be 559nm and your pupil diameter to be 4.69mm. Answer in km!

1. Look at your data in Table 1. What was the last measured temperature before the all ice melted (so it was still mixture of ice and water)?
2. Look at your data in Table 1. Describe what happened to the temperature of the water as during melting process
3. What happened to the temperature of the water after it melted?
4. Based on your observation of temperature during melting process hypothesize how the temperature of the water changed during freezing process.

5. What happened to the temperature of the water, which was placed on the oven top, during the heating process?

6. Look at your data in Table 2. What happened to the temperature of the water after it started boiling?

7. What was the temperature of your boiling water? The standard boiling temperature for water is 100 °C. Does your measurement agree with this? Explain why or why not.

8. Explain why temperature does not change during a phase change. Where does the heat energy go if not into increasing or decreasing temperature?

In what ways does a tightrope walker’s pole increase stability?

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