PHYS 102 Chapter 2 Homework (ERAU)

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PHYS 102 Chapter 2 Homework (ERAU)

1. A jet aircraft with a mass of 4,575 kg has an engine that exerts a force (thrust) equal to 60,200 N.
2. A motorcycle and rider have a total mass equal to 280 kg. The rider applies the brakes, causing the motorcycle to accelerate at a rate of −7 m/s2. What is
   the net force on the motorcycle? (Indicate the direction with the sign of your answer.)
   In an experiment performed in a space station, a force of 29 N causes an object to have an acceleration equal to 5 m/s2. What is the object’s mass?
   On aircraft carriers, catapults are used to accelerate jet aircraft to flight speeds in a short distance. One such catapult takes a 18,400­kg jet from 0 to 69 m/s
   in 2.6 s. (Assume the catapult acts in the positive horizontal direction. Indicate the direction with the sign of your answer where appropriate.)
   An airplane is built to withstand a maximum acceleration of 5 g. If its mass is 1,510 kg, what size force would cause this acceleration?
   Under certain conditions, the human body can safely withstand an acceleration of 10 g.
   (a) What net force would have to act on someone with mass of 54 kg to cause this acceleration?
   A race car rounds a curve at 50 m/s. The radius of the curve is 402 m, and the car’s mass is 665 kg. (Assume the car’s speed remains constant. Take the
   radially inward direction to be positive. Indicate the direction with the sign of your answer.)
   A hang glider and its pilot have a total mass equal to 152 kg. While executing a 360° turn, the glider moves in a circle with a 9 m radius. The glider’s speed is
   12 m/s. (Assume the glider turns along the horizontal plane.)
   As a spacecraft approaches a planet, the rocket engines on it are fired (turned on) to slow it down so it will go into orbit around the planet. The spacecraft’s mass is 2,375 kg and the thrust (force) of the rocket engines is 465 N. If its speed must be decreased by 1,109 m/s, how long (in minutes) must the engines
   As a baseball is being caught, its speed goes from 39 to 0 m/s in about 0.004 s. Its mass is 0.145 kg. (Take the direction the baseball is thrown to be positive.)
   As a rocket ascends, its acceleration increases even though the net force on it stays constant. Why? (Assume a traveling distance small enough that the thrust,
   acceleration due to gravity and atmosphere do not change.)
   A person is riding on a train while watching the display on a GPS unit. The person notices that both the “speed” and the “heading” readings are not changing.
   What can the person conclude about the net force acting on the train car?

PHYS 102 Chapter 3 Homework (ERAU)

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PHYS 102 Chapter 3 Homework (ERAU)

Which has the larger linear momentum: a 2,100­kg houseboat going 8 m/s or a 770­kg speedboat going 25m/s?

A 7,800­kg truck runs into the rear of a 1,000­kg car that was stationary. The truck and car are locked together after the collision and move with speed 4 m/s.

What was the speed of the truck before the collision?

In compressing the spring in a toy dart gun, 0.6 J of work is done. When the gun is fired, the spring gives its potential energy to a dart with a mass of 0.09 kg.

At NASA’s Zero Gravity Research Facility in Cleveland, Ohio, experimental payloads fall freely from rest in an evacuated vertical shaft through a distance of

132 m.

A bicycle and rider going 12 m/s approach a hill. Their total mass is 71 kg.

A 1,000­W motor powers a hoist used to lift cars at a service station.

 running back with a mass of 98 kg and a velocity of 7 m/s (toward the right) collides with, and is held by, a147­kg defensive tackle going in the opposite

direction (toward the left). What is the velocity of the tackle before the collision for their velocity afterward to be zero? (Remember, velocity is a vector)

t takes 120 minutes for a middle­aged physics professor to ride his bicycle up the road to Alpe d’Huez in France. The vertical height of the climb is 1,120 m,

and the combined mass of the rider and bicycle is 81 kg. What is the bicyclist’s average power output?

When you throw a ball, the work you do to accelerate it equals the kinetic energy the ball gains. If you dotwice as much work when throwing the ball, does it

go twice as fast? Explain.

Describe the motion of an object that possesses kinetic energy yet undergoes no net displacement.

If we know that a force of 5 N acts on an object while it moves 2 meters, can we calculate how much work was done with no other information? Explain your

answer .

During a head­on collision between two automobiles, the occupants are decelerated rapidly. Use the idea of work to explain why an air bag that quickly inflates

in front of an occupant reduces the likelihood of injury. (Select all that apply.)

If you hold a ball at eye level and drop it, it will bounce back, but not to its original height. Identify the energy conversions that take place during the process,

and explain why the ball does not reach its original release level.

PHYS 102 Chapter 4 Homework (ERAU)

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PHYS 102 Chapter 4 Homework (ERAU)

The water in the plumbing in a house is at a gauge pressure of 210,000 Pa. What force does this cause on the top of the tank inside a water heater if the area

of the top is 0.5 m2? (Ignore atmospheric pressure.)

A viewing window on the side of a large tank at a public aquarium measures 51 in. by 61 in. The average gauge pressure from the water is 7 psi. What is the

total outward force on the window?

A small statue is recovered in an archaeological dig. Its weight is measured to be 34.3 lb and its volume 0.07ft3.

A certain part of an aircraft engine has a volume of 1.9 ft3.

The depth of the Pacific Ocean in the Mariana Trench is 36,198 ft. What is the gauge pressure at this depth?

A storage tank 22 m high is filled with pure water. (Assume the tank is open and exposed to the atmosphere at the top.)

A modern­day zeppelin holds 7,100 m3 of helium. Compute its maximum payload at sea level. (Assume the helium and air to be at 0°C and 1 atm.)

A juniper­wood plank measuring 0.47 ft by 1 ft by 12 ft is totally submerged in water.

A rectangular block of ice with dimensions 2 m by 2 m by 0.3 m floats on water. A person weighing 845 N wants to stand on the ice. Would the ice sink below the surface of the water?

The wing of an airplane has an average cross­sectional area of 14 m2 and experiences a lift force of 80,000N. What is the average difference in the air pressure (in N/m^2)between the top and bottom of the wing?

Describe the four phases of matter. Compare their external, observable properties.

Why is it that a person can lay still on a “bed” of nails (see the figure below) without suffering any serious injuries but would incur severe puncture wounds to

his feet if he tried to stand barefoot on the same “bed”?

Would the weight density of water be different on the Moon than it is on Earth?

The pressure in the air along the upper surface of an aircraft’s wing (in flight) is lower than the pressure along the lower surface. Compare the speed of the air

flowing over the wing to that of the air flowing under the wing.

PHYS 102 Chapter 5 Homework (ERAU)

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PHYS 102 Chapter 5 Homework (ERAU)

On a nice winter day at the South Pole, the temperature rises to −32°F. What is the approximate temperature in degrees Celsius?

An iron vat is 19 m long at room temperature (20°C). How much longer is it when it contains boiling water at 1 atm pressure?

A bottle containing 2 kg of water at a temperature of 15°C is placed in a refrigerator where the temperature is kept at 2°C. How much heat is transferred from the water to cool it to 2°C?

A 0.04­kg lead bullet traveling 290 m/s strikes an armor plate and comes to a stop. If all of the bullet’s energy is converted to heat that it alone absorbs, what is its temperature change?

One cubic meter of water (see Table 4.4 for the mass density of water) flowing over the Upper Falls in Yellowstone National Park drops 33 m. If all of the water’s potential energy is converted to kinetic energy at the bottom of the falls and the kinetic energy goes to heat the water, what is the temperature increase of the water?

What is the maximum efficiency that a heat engine could have when operating between the normal boiling and freezing temperatures of water?

A proposed ocean thermal­energy conversion (OTEC) system is a heat engine that would operate between warm water (24°C) at the ocean’s surface and cooler water (4°C) 1,706 m below the surface. What is the maximum possible efficiency of the system? Enter your answer accurate to two decimal places.

What is the significance of absolute zero?

What happens to the atoms and molecules in a substance as its temperature increases?

Air molecules in a warm room (27°C = 300 K) typically have speeds of about 500 m/s (1,100 mph). Why is it that we are unaware of these fast­moving

particles continuously colliding with our bodies?

An aluminum wing on a passenger jet is 36 m long when its temperature is 22°C. At what temperature would the wing be 6 cm (0.06 m) shorter?

Air in a balloon does 43 J of work while absorbing 74 J of heat. What is its change in internal energy?

What is unusual about the behavior of water below the temperature of 4°C?

Is it possible to compress air without causing its internal energy to increase?

PHYS 102 Chapter 6 Homework (ERAU)

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PHYS 102 Chapter 6 Homework (ERAU)

The force stretching the D string on a certain guitar is 131 N. The string’s linear mass density is 0.006 kg/m. What is the speed of the waves on the string?

The coldest and hottest temperatures ever recorded in Switzerland are −43.2°F (231 K) and 106.7°F (315 K), respectively. What is the speed of sound in air at each temperature?

A 800­Hz sound travels through pure neon. The wavelength of the sound is measured to be 0.54 m. What is the speed of sound in neon?

What frequency of sound traveling in air at 20°C has a wavelength equal to 1.8 m, the average height of a person?

What is the wavelength (in mm) of 2 million Hz ultrasound as it travels through human tissue?

The huge volcanic eruption on the island of Krakatoa, Indonesia, in 1883 was heard on Rodrigues Island, 4,782 km (2,970 miles) away. How long did it take (in seconds) for the sound to travel to Rodrigues? (Assume the air temperature is 20°C.)

A steel cable with total length 64 m and mass 130 kg is connected to two poles. The tension in the cable is1,661 N, and the wind makes the cable vibrate with a frequency of 2 Hz. Calculate the wavelength of the resulting wave on the cable.

A geologist is camped 4,834 m (about 3 miles) from a volcano as it erupts.

A person stands at a point 219 m in front of the face of a sheer cliff. If the person shouts, how much time will elapse before an echo is heard? (Assume the

speed of sound is 344 m/s.)

The sound level measured in a room by a person watching a movie on a home theater system varies from 40dB during a quiet part to 80 dB during a loud part. Approximately how many times louder is the latter sound? (enter only a number as your answer)

Give an example of a wave that does not need a medium in which to travel and a wave that does need a medium.

The speed of an aircraft is sometimes expressed as a Mach number: Mach 1 means that the speed is equal to the speed of sound. If you wish to determine the

speed of an aircraft going Mach 2.2, for example, in meters per second or miles per hour, what additional information do you need?

If you were actually in a battle fought in space like the ones shown in science fiction movies, would you hear the explosions that occur?

A low­frequency sound is heard, and then a high­frequency sound is heard. Which sound has a longer wavelength?

A person riding on a bus hears the sound from a horn on a car that is stopped.What is different about the sound when the bus is approaching the car compared

to when the bus is moving away from the car ?

PHYS 102 Chapter 7 Homework (ERAU)

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PHYS 102 Chapter 7 Homework (ERAU)

A current of 20.4 A flows through an electric heater operating on 120 V. What is the heater’s resistance?

A 340 Ω resistor is connected to a variable­voltage power supply.

A current of 11.0 A flows through an electric heater operating on 120 V. Compute the power consumption of the electric heater.

An electric train operates on 890 V. What is its power consumption when the current flowing through the train’s motor is 2,030 A?

All of the electrical outlets in a room are connected in a single parallel circuit. The circuit is equipped with a 20 A fuse, and the voltage is V = 220 V.

Your cell phone typically consumes about 330 mW of power when you text a friend. If the phone is operated using a lithium­ion battery with a voltage of 3.5 V, what is the current flowing through the cell­phone circuitry under these circumstances?

An electric clothes dryer is rated at 2,400 W. How much energy does it use in 20 min?

A certain electric motor draws a current of 78 A when connected to 120 V.

An electric car is being designed to have an average power output of 6,700 W for 2 h before needing to be recharged. (Assume there is no wasted energy.)

A solid metal cylinder has a certain resistance. It is then heated and carefully stretched to form a longer, thinner cylinder. After it cools, will its resistance be

the same as, greater than, or less than what it was before?

If a new material is found that is a superconductor at all temperatures, what parts of some common electric devices would definitely not be made out of it?

(Select all that apply.)

A simple electric circuit consists of a constant­voltage power supply and a variable resistor. What effect does reducing the resistance have on the current in the

circuit and on the power output of the power supply?

What is the purpose of having fuses or circuit breakers in electric circuits? How should they be connected in circuits so they will be effective?

A 20­A fuse in a household electric circuit burns out. What catastrophe could occur if it is replaced by a 30­A fuse?

PHYS 102 Chapter 8&9 Homework (ERAU)

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PHYS 102 Chapter 8&9 Homework (ERAU)

The generator at a power plant produces AC at 22,000 V. A transformer steps this up to 295,000 V for transmission over power lines. If there are 2,200 turns of wire in the input coil of the transformer, how many turns must there be in the output coil?

What is the wavelength of the 46,000­Hz radio wave used by “radio­controlled” clocks and wristwatches?

A piece of iron is heated with a torch to a temperature of 558 K. How much more energy does it emit as blackbody radiation at 558 K than it does at room temperature, 295 K?

What is the wavelength of the peak of the blackbody radiation curve for the human body (T = 311 K)? (Enter your answer to at least two decimal places.)

The blackbody radiation emitted from a furnace peaks at a wavelength of 6.2 10­6 m (0.0000062 m). What is the temperature inside the furnace?

The wavelength of an electromagnetic wave is measured to be 5.40 10­7 m.

A small object is placed to the left of a convex lens and on its optical axis. The object is 30 cm from the lens, which has a focal length of 19 cm. If the object is moved to a position 28 cm to the left of the lens, what will the image position be? (A positive value for p, or position, means the image is on the right side of the lens.)

A camera is equipped with a lens with a focal length of 31 cm. When an object 1.1 m (110 cm) away is being photographed, what is the magnification?

Aircraft equipped with powerful radar units are forbidden from turning them on when on the ground near people. Explain why this is so.

Which type of EM wave does your body emit most strongly?

Stars emit radiation whose spectrum is very similar to that of a blackbody. Imagine two stars identical in size, each of which is at the same distance from us. One of the stars appears reddish in color, while the other one looks distinctly bluish. Based on this information, what can you say about the relative temperatures of the two stars? Which is the hotter?

Describe the greenhouse effect that is occurring in the Earth’s atmosphere.

How does the ionosphere affect the range of radio communications?