Physics Homework Help Please. Can You Review My Answers ?
May 19th, 2009
1. Many people are considering using solar power for their residence. Cost is typcially computed by the number of square meters of solar panels required. To figure this number out, think about the following:
1) A commercial solar cell array can convert sunlight to an average power
output of about 20 Watts per square meter of solar cells (this is averaged over day and night, year round).
2) a typical home requires about 8,750 kw-hrs of energy per year.
so, given this information, How many square meters of solar panels would be required to provide a home with 8,750 kilowatt hours of electricity in a year?
a
b
c
d
I believe the answer is 100.
2. According to Kepler’s famous second law, any body (such as a comet) orbiting the sun in an elliptical orbit moves fastest when it is closest to the sun and slowest when it is farthest. In terms of energy, which of the following statements correctly describes what’s happening?
a comet’s kinetic energy is greatest when it is closest to the sun, but its total energy stays constant no matter where it is in its orbit.
b comet’s potential energy is greatest when it is closest to the sun, but its total energy stays constant no matter where it is in its orbit.
c comet’s total energy is greatest when it is closest to the sun, and least when it is farthest
d comet has escape velocity from its orbit about the sun
I selected answer b.
3. Two shopping carts, one filled with ten bricks and one filled with twenty bricks are pushed by identical twin shoppers with equal forces over equal distances until they get to the edge of a parking lot. Which cart will have the great speed at the edge?
a cart with 10 bricks
b cart with 20 bricks
c the same
I selected answer b. the cart with 20 bricks
4. Envision an astronaut on the inside of a rotating wheel (i. a massive rotating space station). he’ll feel a force of contact between his feet and ground, and and objects that she drops will accelerte towards the floor (where her feet are planeted). Is this possible, and why?
a.There’s no outward force. His inertia, and the inertia of anyting else simply causes her to move outward towards the floor,and the floor pushes back.
b.There’s an outwardly directed force called a centrifugal force c can only occur is the space station is so big that a gravitational force between the walls of the space station and the astronaut pull her to the floor.
I’m not sure about this answer. Please help :)
d will only occur when the floor of the space station is directly above the Earth
5. Envision you’ve a rotating disk that’s spinning at a constant rate. Also envision that an ant has crawled to the edge of the disk, and a spider is sitting at a point halfway between the center and edge
a spider and the ant both have the same liner speed, but the angular speed of the spider is twice that of the ant.
b Spider has half the angular speed of the ant, but twice the linier speed.
c spider and the ant have the same angular speed, but the ant has twice the linier speed as the spider.
d have the same angular speed and the same linier speed.
I selected answer b.
6. Approximately how many times will you’ve to lift a one kilogram
book one meter over your head to do one kilowatt hour of work?
36
360
3600
36000
360000
7. Envision you’re pushing on a door that’s shut but can swing freely. If you push at one end, a distance of 1 meters from the the door hinge, the door begins to swing with an angular accleration of 1 radians per second squared. If you instead push (with the same force and the same angle) at distance of 1 meters from the door hinge, what will be the angular accelration of the door?
about 1 rad/s/s
about 2 rad/s/s
It will be exactly the same: 1 rad/s/s
You’ll not be able to move the door
I selected answer 2 rad/s/s
8. According to a treadmill at a nearby athletic club, a person of average weight (i. your physics instructor) running a 10 minute mile expends energy at a rate of 200 Watts. At this rate, how long would it take to burn off 100 Calories (equalivant to a cup of frozen yogurt ingested just after workout). Note that a food Calorie is also called a Kilocalorie and one kilocalorie is equivilant to 4,186 joules, so the cup of yogurt contains 481,600 Joules. Note that your answer will probably be quite different than the “calorie count” on a treadmill!
about 10 minutes (600 seconds)
about 25 minutes ( 1500 seconds)
about 35 minutes ( 2100 s)
about an hour (3600 s)
I selected answer about 25 minutes
9. When an ice skater moves her arms outward, her angular speed decreases becuase:
Her angular momentum decreases
Her moment of inertia increases but her angular momentum stays
Thanks I really want to pass this class.
1) A commercial solar cell array can convert sunlight to an average power
output of about 20 Watts per square meter of solar cells (this is averaged over day and night, year round).
2) a typical home requires about 8,750 kw-hrs of energy per year.
so, given this information, How many square meters of solar panels would be required to provide a home with 8,750 kilowatt hours of electricity in a year?
a
b
c
d
I believe the answer is 100.
2. According to Kepler’s famous second law, any body (such as a comet) orbiting the sun in an elliptical orbit moves fastest when it is closest to the sun and slowest when it is farthest. In terms of energy, which of the following statements correctly describes what’s happening?
a comet’s kinetic energy is greatest when it is closest to the sun, but its total energy stays constant no matter where it is in its orbit.
b comet’s potential energy is greatest when it is closest to the sun, but its total energy stays constant no matter where it is in its orbit.
c comet’s total energy is greatest when it is closest to the sun, and least when it is farthest
d comet has escape velocity from its orbit about the sun
I selected answer b.
3. Two shopping carts, one filled with ten bricks and one filled with twenty bricks are pushed by identical twin shoppers with equal forces over equal distances until they get to the edge of a parking lot. Which cart will have the great speed at the edge?
a cart with 10 bricks
b cart with 20 bricks
c the same
I selected answer b. the cart with 20 bricks
4. Envision an astronaut on the inside of a rotating wheel (i. a massive rotating space station). he’ll feel a force of contact between his feet and ground, and and objects that she drops will accelerte towards the floor (where her feet are planeted). Is this possible, and why?
a.There’s no outward force. His inertia, and the inertia of anyting else simply causes her to move outward towards the floor,and the floor pushes back.
b.There’s an outwardly directed force called a centrifugal force c can only occur is the space station is so big that a gravitational force between the walls of the space station and the astronaut pull her to the floor.
I’m not sure about this answer. Please help :)
d will only occur when the floor of the space station is directly above the Earth
5. Envision you’ve a rotating disk that’s spinning at a constant rate. Also envision that an ant has crawled to the edge of the disk, and a spider is sitting at a point halfway between the center and edge
a spider and the ant both have the same liner speed, but the angular speed of the spider is twice that of the ant.
b Spider has half the angular speed of the ant, but twice the linier speed.
c spider and the ant have the same angular speed, but the ant has twice the linier speed as the spider.
d have the same angular speed and the same linier speed.
I selected answer b.
6. Approximately how many times will you’ve to lift a one kilogram
book one meter over your head to do one kilowatt hour of work?
36
360
3600
36000
360000
7. Envision you’re pushing on a door that’s shut but can swing freely. If you push at one end, a distance of 1 meters from the the door hinge, the door begins to swing with an angular accleration of 1 radians per second squared. If you instead push (with the same force and the same angle) at distance of 1 meters from the door hinge, what will be the angular accelration of the door?
about 2 rad/s/s
It will be exactly the same: 1 rad/s/s
You’ll not be able to move the door
8. According to a treadmill at a nearby athletic club, a person of average weight (i. your physics instructor) running a 10 minute mile expends energy at a rate of 200 Watts. At this rate, how long would it take to burn off 100 Calories (equalivant to a cup of frozen yogurt ingested just after workout). Note that a food Calorie is also called a Kilocalorie and one kilocalorie is equivilant to 4,186 joules, so the cup of yogurt contains 481,600 Joules. Note that your answer will probably be quite different than the “calorie count” on a treadmill!
about 10 minutes (600 seconds)
about 25 minutes ( 1500 seconds)
about 35 minutes ( 2100 s)
about an hour (3600 s)
I selected answer about 25 minutes
9. When an ice skater moves her arms outward, her angular speed decreases becuase:
Her angular momentum decreases
Her moment of inertia increases but her angular momentum stays
Thanks I really want to pass this class.
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