Fire hoses used in major structure fires have inside diameters of 2.500 in (1 in = 2.54 cm). The nozzle of the fire hose have an inside diameter of 1.200 in. When firefighters are fighting a fire 2020.007 cm above the ground, the pressure in the nozzle is less than at ground level. When measured, the gauge pressure in the nozzle is 0.000 Pa.

(a) How are the firefighters able to fight a fire with zero water pressure? Explain your answer.

(b) What is the value of the water pressure as it emerges into the air from the nozzle? Explain your answer

1a. A positive particle of charge 5 C sits stationary [locked to the ground] 3.5 meters from a negatively charged particle, with charge 2 C. How strong is the force the negative particle experiences? How does that compare if the negative particle is 7 meters away? Both charges have mass of 5 grams; how fast does the negatively charged particle accelerate in both cases?

b. What force does a particle with a charge of +5 C, moving at 10 m/s feel when moving *perpendicular* to a 3 Tesla magnetic field? What about if it moves parallel to the field?

c.Which process will produce a higher energy form of light? A free electron being captured at the n = 2 energy level, or n = 1?

1. Does the emf induced by a changing magnetic flux depend on the resistance of the circuit?
2. A plastic frisbee is fitted with a metal ring around its rim. If the frisbee is thrown, does the Earth's magnetic field induce an emf? Explain.
3. Suppose that the frisbee in question # 3 is thrown so that it tumbles. In this case does the Earth's magnetic field induce an emf? Explain.
4. At the equator, the direction of the Earth's magnetic field is north. Suppose you are at the equator, driving north in our car. If you make a turn, will there be an induced current in the metal loop that frames your windshield?
5. What is the direction of the induced current in the loop in question # 5 (clockwise or counterclockwise from your perspective)?

Two forces, F⃗ 1 and F⃗ 2, act at a point. F⃗ 1 has a magnitude of 8.20 N and is directed at an angle of 64.0 ∘ above the negative x axis in the second quadrant. F⃗ 2has a magnitude of 5.20 N and is directed at an angle of 53.8 ∘ below the negative x axis in the third quadrant.

Part A

What is the x component of the resultant force?

Part B

What is the y component of the resultant force?

Express your answer in newtons.

Part C

What is the magnitude of the resultant force?

A "Carnot" refrigerator (reverse of a Carnot engine) absorbs heat from the freezer compartment at a temperature of -17

A neutral conducting sphere is suspended from a thin insulating thread (don't ignore gravity in this problem). A charged insulating rod is brought near the sphere, but the rod and sphere do not touch. How will the sphere react to the presence of the rod?

A .5 kg air puck moves to the right at 3 m/s, colliding with a 1.5kg air puck that is moving to the left at 1.5 m/s.

1. Determine the direction and speed of the pucks' motion if they stick to each other after the collision.  

2. Suppose instead that the pucks do not stick together. If the 1.5kg puck moves to the right at .231 m/s after the collision, was the collision elastic? Provide evidence!

3. Determine the size and direction of the average force acting on the .5kg puck during the second collision, if the collision lasted for 25 ms.

What is the difference between a refrigerator and a heat pump? What is the difference between a refrigerator and an air conditioner? Define the coefficient of performance of a refrigerator in words. Can it be greater than unity? Check the specification of refrigerator or air-conditioner at your home. See if you can obtain COP of the machine. A heat pump that is used to heat a house has a COP of 2.5. That is, the heat pump delivers 2.5 kWh of energy to the house for each 1 kWh of electricity it consumes. Is this a violation of the first law of thermodynamics? Explain.

Explain carefully what is meant by effective mass in the context of semiconductor physics. The energy band dispersion relation (E vs. k) for a simple one-dimensional monatomic semiconductor of lattice constant a can be written-

? = ?₀ [1 − cos(??)]

Derive an expression for the effective mass (m*) of an electron in the semiconductor, and sketch how m* varies as a function of k.

A 3 kg cat can jump at 3 m/s. The cat rests on an 8 kg sled(A), then jumps to another 8 kg sled(B). The cat immediately spins around and jumps back to the first sled(A). The sleds are on a frictionless surface.

a. What is the final speed of sled(A)?

b. What is the final speed of sled(B)?

c. What total impulse was imparted to sled(B)?

d. What was the overall change in momentum of sled(A)?

You see a dead squirrel in your yard. You do not know if it was electrocuted (source AC) or hit by lightning (source DC). Is there any way to find out (after performing autopsy on it) whether it was AC or DC which caused its death. Explain

An object of mass 4.15 kg undergoes an acceleration of 3.5 m/s^2 for a period of 7.0 seconds. It then undergoes an acceleration of -4.2 m/s^2 for a period of 18.0 seconds. If the initial velocity of the object is 4.01 m/s and it first experiences the acceleration when it is at the origin, plot by hand on graph paper (to scale) the force, velocity, and position graphs as functions of time. Explain why your graphs look the way they do and include all relevant equations.

1. Two spheres, one solid, one a thin shell, each have a mass of 0.89 kg and a radius of 11 cm. They are given the same torque of 0.13 mN acting for 7 s. Which sphere is rotating faster?

A 160-V battery is connected across two parallel metal plates of area 28.5 cm^2 and separation 8.10 mm . A beam of alpha particles (charge +2e, mass 6.64×10^−27kg) is accelerated from rest through a potential difference of 1.60 kV and enters the region between the plates perpendicular to the electric field.

Part A: What magnitude of magnetic field is needed so that the alpha particles emerge undeflected from between the plates?

Part B: What direction of magnetic field is needed so that the alpha particles emerge undeflected from between the plates if the charges are moving to the right and the electric field points upward?