I have had no luck with my previous answers on modules 1-3, and I have started module-4, and the answers to the first two questions are both wrong. I am spending all this money and receiving very little help. Can you please assist me? The exercise questions are from Centage PHY-101.

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1.

[0/4 Points]DETAILSPREVIOUS ANSWERSOSCOLPHYS2016 7.1.P.001.

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How much work does a supermarket checkout attendant do on a can of soup he pushes0.750m horizontally with a force of5.50N?Express your answer in joules and kilocalories.

J kcal

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2.

[0/4 Points]DETAILSPREVIOUS ANSWERSOSCOLPHYS2016 7.1.P.004.

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Suppose a car travels 108 km at a speed of25.0m/s, and uses2.10gallons of gasoline. Only 30% of the gasoline goes into useful work by the force that keeps the car moving at constant speed despite friction. (The energy content of gasoline is1.3010⁸Jper gallon.)

(a)

What is the force (in N) exerted to keep the car moving at constant speed?

N

(b)

If the required force is directly proportional to speed, how many gallons will be used to drive 108 km at a speed of28.0 m/s?

gallons

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3.

[-/4 Points]DETAILSOSCOLPHYS2016 7.2.P.012.

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(a)

Calculate the force (in N) needed to bring a1100kg car to rest from a speed of95.0km/h in a distance of100m(a fairly typical distance for a non-panic stop).

N

(b)

Suppose instead the car hits a concrete abutment at full speed and is brought to a stop in2.00 m.Calculate the force exerted on the car and compare it with the force found in part (a).

force in (b)

force in (a)

=

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4.

[-/4 Points]DETAILSOSCOLPHYS2016 7.2.P.013.

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A car's bumper is designed to withstand a6.84km/h (1.9-m/s) collision with an immovable object without damage to the body of the car. The bumper cushions the shock by absorbing the force over a distance. Calculate the magnitude of the average force on a bumper that collapses0.150mwhile bringing a860kgcar to rest from an initial speed of1.9m/s.

N

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5.

[-/4 Points]DETAILSOSCOLPHYS2016 7.3.P.017.

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(a)

How much gravitational potential energy (in J) (relative to the ground on which it is built) is stored in an Egyptian pyramid, given its mass is about910⁹kgand its center of mass is51.0mabove the surrounding ground?

J

(b)

What is the ratio of this energy to the daily food intake of a person (1.210⁷J)?

:1

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6.

[-/4 Points]DETAILSOSCOLPHYS2016 7.3.P.021.

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In a downhill ski race, surprisingly, little advantage is gained by getting a running start. (This is because the initial kinetic energy is small compared with the gain in gravitational potential energy even on small hills.) To demonstrate this, find the final speed in m/s and the time taken in seconds for a skier who skies67.0malong a27slopeneglecting friction for the following two cases. (Enter the final speeds to at least one decimal place.)

(a)

starting from rest

final speed m/stime taken s

(b)

starting with an initial speed of3.40m/s

final speed m/stime taken s

(c)

Does the answer surprise you? Discuss why it is still advantageous to get a running start in very competitive events.

This answer has not been graded yet.

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7.

[-/4 Points]DETAILSOSCOLPHYS2016 7.4.P.022.

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A6.5010⁵kg subway train is brought to a stop from a speed of 0.500 m/s in0.800m by a large spring bumper at the end of its track. What is the force constantkof the spring (in N/m)?

N/m

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8.

[-/4 Points]DETAILSOSCOLPHYS2016 7.5.P.024.

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A50.0kg skier with an initial speed of14.0m/s coasts up a2.50 mhigh rise as shown in the following figure.

Find her final speed at the top (in m/s), given that the coefficient of friction between her skis and the snow is 0.0800. (Hint: Find the distance traveled up the incline assuming a straight-line path as shown in the figure.)

m/s

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9.

[-/4 Points]DETAILSOSCOLPHYS2016 7.7.P.032.

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A person in good physical condition can put out 100 W of useful power for several hours at a stretch, perhaps by pedaling a mechanism that drives an electric generator. Neglecting any problems of generator efficiency and practical considerations such as resting time, answer the following.

(a)

How many people would it take to run a4.00kW electric clothes dryer?

people

(b)

How many people would it take to replace a large electric power plant that generates600MW?

people

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10.

[-/4 Points]DETAILSOSCOLPHYS2016 7.8.P.047.

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(a)

What is the efficiency of an out-of-condition professor who does2.3010⁵J of useful work while metabolizing510kcal of food energy?

%

(b)

How many food calories (in kcal) would a well-conditioned athlete metabolize in doing the same work with an efficiency of15%?

kcal