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Calculate the power output needed for a 950-kg car to climb a 2.00 ° slope at a constant 30.0 m/s while encountering wind resistance and friction totaling 600 N.

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A man of mass 80 kg runs up a flight of stairs 20 m high in 10 s. (a) how much power is used to lift the man? (b) If the man’s body is 25% efficient, how much power does he expend?

a. 1.57 kW; b. 6.28 kW

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The man of the preceding problem consumes approximately 1.05 × 10 7 J (2500 food calories) of energy per day in maintaining a constant weight. What is the average power he produces over a day? Compare this with his power production when he runs up the stairs.

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An electron in a television tube is accelerated uniformly from rest to a speed of 8.4 × 10 7 m/s over a distance of 2.5 cm. What is the power delivered to the electron at the instant that its displacement is 1.0 cm?

6.83 μW

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Coal is lifted out of a mine a vertical distance of 50 m by an engine that supplies 500 W to a conveyer belt. How much coal per minute can be brought to the surface? Ignore the effects of friction.

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A girl pulls her 15-kg wagon along a flat sidewalk by applying a 10-N force at 37 ° to the horizontal. Assume that friction is negligible and that the wagon starts from rest. (a) How much work does the girl do on the wagon in the first 2.0 s. (b) How much instantaneous power does she exert at t = 2.0 s ?

a. 8.51 J; b. 8.51 W

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A typical automobile engine has an efficiency of 25%. Suppose that the engine of a 1000-kg automobile has a maximum power output of 140 hp. What is the maximum grade that the automobile can climb at 50 km/h if the frictional retarding force on it is 300 N?

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When jogging at 13 km/h on a level surface, a 70-kg man uses energy at a rate of approximately 850 W. Using the facts that the “human engine” is approximately 25% efficient, determine the rate at which this man uses energy when jogging up a 5.0 ° slope at this same speed. Assume that the frictional retarding force is the same in both cases.

1.7 kW

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Additional problems

A cart is pulled a distance D on a flat, horizontal surface by a constant force F that acts at an angle θ with the horizontal direction. The other forces on the object during this time are gravity ( F w ), normal forces ( F N 1 ) and ( F N 2 ), and rolling frictions F r 1 and F r 2 , as shown below. What is the work done by each force?

The figure is an illustration of cart being pulled with a force F applied up and to the right at an angle of theta above the horizontal. The displacement is horizontally to the right. The force F sub w acts vertically downward at the center of the cart. Force F sub N 1 acts vertically upward on the rear wheel. Force F sub r 1 acts to horizontally the left on the rear wheel. Force F sub N 2 acts vertically upward on the front wheel. Force F sub r 2 acts horizontally to the left on the front wheel.
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Consider a particle on which several forces act, one of which is known to be constant in time: F 1 = ( 3 N ) i ^ + ( 4 N ) j ^ . As a result, the particle moves along the x -axis from x = 0 to x = 5 m in some time interval. What is the work done by F 1 ?

15 N · m

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Consider a particle on which several forces act, one of which is known to be constant in time: F 1 = ( 3 N ) i ^ + ( 4 N ) j ^ . As a result, the particle moves first along the x -axis from x = 0 to x = 5 m and then parallel to the y -axis from y = 0 to y = 6 m . What is the work done by F 1 ?

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Consider a particle on which several forces act, one of which is known to be constant in time: F 1 = ( 3 N ) i ^ + ( 4 N ) j ^ . As a result, the particle moves along a straight path from a Cartesian coordinate of (0 m, 0 m) to (5 m, 6 m). What is the work done by F 1 ?

39 N · m

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Questions & Answers

the diagram of the digestive system
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How does twins formed
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They formed in two ways first when one sperm and one egg are splited by mitosis or two sperm and two eggs join together
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Genetics is the study of heredity
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the study of living organisms and their interactions with one another and their environments
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the study of living organisms and their interactions with one another and their environment.
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list any five characteristics of the blood cells
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advantage of electronic microscope is easily and clearly while disadvantage is dangerous because its electronic. advantage of light microscope is savely and naturally by sun while disadvantage is not easily,means its not sharp and not clear
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cells is the basic structure and functions of all living things
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is organisms that are similar into groups called tara
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in what situation (s) would be the use of a scanning electron microscope be ideal and why?
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A scanning electron microscope (SEM) is ideal for situations requiring high-resolution imaging of surfaces. It is commonly used in materials science, biology, and geology to examine the topography and composition of samples at a nanoscale level. SEM is particularly useful for studying fine details,
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Diversity of living thing
ISCONT
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Cell division is the process by which a single cell divides into two or more daughter cells. It is a fundamental process in all living organisms and is essential for growth, development, and reproduction. Cell division can occur through either mitosis or meiosis.
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life is defined as any system capable of performing functions such as eating, metabolizing,excreting,breathing,moving,Growing,reproducing,and responding to external stimuli.
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Source:  OpenStax, University physics volume 1. OpenStax CNX. Sep 19, 2016 Download for free at http://cnx.org/content/col12031/1.5
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