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A cartoon shows the toupee coming off the head of an elevator passenger when the elevator rapidly stops during an upward ride. Can this really happen without the person being tied to the floor of the elevator? Explain your answer.

Problem exercises

A flea jumps by exerting a force of 1 . 20 × 10 5 N size 12{1 "." "20" times "10" rSup { size 8{ - 5} } " N"} {} straight down on the ground. A breeze blowing on the flea parallel to the ground exerts a force of 0 . 500 × 10 6 N size 12{0 "." "500" times "10" rSup { size 8{ - 6} } " N"} {} on the flea. Find the direction and magnitude of the acceleration of the flea if its mass is 6 . 00 × 10 7 kg size 12{6 "." "00" times "10" rSup { size 8{ - 7} } " kg"} {} . Do not neglect the gravitational force.

10.2 m/s 2 , 4.67º from vertical size 12{"10" "." 2" m/s" rSup { size 8{2} } ", 4" "." "68"°" from vertical"} {}

Two muscles in the back of the leg pull upward on the Achilles tendon, as shown in [link] . (These muscles are called the medial and lateral heads of the gastrocnemius muscle.) Find the magnitude and direction of the total force on the Achilles tendon. What type of movement could be caused by this force?

An Achilles tendon is shown in the figure with two forces acting upward, one at an angle of plus twenty degrees, one at minus twenty degrees. F sub one, equal to two hundred newtons, is shown by a vector making an angle twenty degrees toward the right with the vertical, and F sub two, equal to two hundred newtons, is shown making an angle of twenty degrees left from the vertical.
Achilles tendon

A 76.0-kg person is being pulled away from a burning building as shown in [link] . Calculate the tension in the two ropes if the person is momentarily motionless. Include a free-body diagram in your solution.

An object of mass m is shown being pulled by two ropes. Tension T sub two acts toward the right at an angle of ten degrees above the horizontal. Another rope makes an angle fifteen degrees to the left of the vertical direction, and tension in the rope is T sub one, shown by a vector arrow. Weight w is acting vertically downward.

T 1 = 736 N size 12{T rSub { size 8{1} } ="736"" N"} {}

T 2 = 194 N size 12{T rSub { size 8{2} } ="194 N"} {}

A lady is being pulled away from a burning building using a rope. She is in the middle of the rope; her weight is shown by a vector acting vertically downward. Tension, T sub one, acts upward through the left side of the rope, making an angle of fifteen degrees with the vertical. Tension T sub two acts through the right side of the rope, making an angle of ten degrees above the positive x axis.
The force T 2 size 12{T rSub { size 8{2} } } {} needed to hold steady the person being rescued from the fire is less than her weight and less than the force T 1 size 12{T rSub { size 8{1} } } {} in the other rope, since the more vertical rope supports a greater part of her weight (a vertical force).

Integrated Concepts A 35.0-kg dolphin decelerates from 12.0 to 7.50 m/s in 2.30 s to join another dolphin in play. What average force was exerted to slow him if he was moving horizontally? (The gravitational force is balanced by the buoyant force of the water.)

Integrated Concepts When starting a foot race, a 70.0-kg sprinter exerts an average force of 650 N backward on the ground for 0.800 s. (a) What is his final speed? (b) How far does he travel?

(a) 7.43 m/s size 12{7 "." "43"" m/s"} {}

(b) 2.97 m

Integrated Concepts A large rocket has a mass of 2 . 00 × 10 6 kg size 12{2 "." "00" times "10" rSup { size 8{6} } " kg"} {} at takeoff, and its engines produce a thrust of 3 . 50 × 10 7 N size 12{3 "." "50" times "10" rSup { size 8{7} } " N"} {} . (a) Find its initial acceleration if it takes off vertically. (b) How long does it take to reach a velocity of 120 km/h straight up, assuming constant mass and thrust? (c) In reality, the mass of a rocket decreases significantly as its fuel is consumed. Describe qualitatively how this affects the acceleration and time for this motion.

Integrated Concepts A basketball player jumps straight up for a ball. To do this, he lowers his body 0.300 m and then accelerates through this distance by forcefully straightening his legs. This player leaves the floor with a vertical velocity sufficient to carry him 0.900 m above the floor. (a) Calculate his velocity when he leaves the floor. (b) Calculate his acceleration while he is straightening his legs. He goes from zero to the velocity found in part (a) in a distance of 0.300 m. (c) Calculate the force he exerts on the floor to do this, given that his mass is 110 kg.

(a) 4.20 m/s size 12{4 "." "20"" m/s"} {}

(b) 29.4 m/s 2 size 12{"29" "." 4" m/s" rSup { size 8{2} } } {}

(c) 4 . 31 × 10 3 N size 12{4 "." "31" times "10" rSup { size 8{3} } " N"} {}

Integrated Concepts A 2.50-kg fireworks shell is fired straight up from a mortar and reaches a height of 110 m. (a) Neglecting air resistance (a poor assumption, but we will make it for this example), calculate the shell’s velocity when it leaves the mortar. (b) The mortar itself is a tube 0.450 m long. Calculate the average acceleration of the shell in the tube as it goes from zero to the velocity found in (a). (c) What is the average force on the shell in the mortar? Express your answer in newtons and as a ratio to the weight of the shell.

Integrated Concepts Repeat [link] for a shell fired at an angle 10.0º size 12{"10" "." 0°} {} from the vertical.

(a) 47.1 m/s

(b) 2 . 47 × 10 3 m/s 2 size 12{2 "." "47" times "10" rSup { size 8{3} } " m/s" rSup { size 8{2} } } {}

(c) 6.18 × 10 3 N . The average force is 252 times the shell’s weight.

Integrated Concepts An elevator filled with passengers has a mass of 1700 kg. (a) The elevator accelerates upward from rest at a rate of 1 . 20 m/s 2 size 12{1 "." "20 m/s" rSup { size 8{2} } } {} for 1.50 s. Calculate the tension in the cable supporting the elevator. (b) The elevator continues upward at constant velocity for 8.50 s. What is the tension in the cable during this time? (c) The elevator decelerates at a rate of 0 . 600 m/s 2 size 12{0 "." "600 m/s" rSup { size 8{2} } } {} for 3.00 s. What is the tension in the cable during deceleration? (d) How high has the elevator moved above its original starting point, and what is its final velocity?

Unreasonable Results (a) What is the final velocity of a car originally traveling at 50.0 km/h that decelerates at a rate of 0 . 400 m/s 2 size 12{0 "." "400 m/s" rSup { size 8{2} } } {} for 50.0 s? (b) What is unreasonable about the result? (c) Which premise is unreasonable, or which premises are inconsistent?

Unreasonable Results A 75.0-kg man stands on a bathroom scale in an elevator that accelerates from rest to 30.0 m/s in 2.00 s. (a) Calculate the scale reading in newtons and compare it with his weight. (The scale exerts an upward force on him equal to its reading.) (b) What is unreasonable about the result? (c) Which premise is unreasonable, or which premises are inconsistent?

Questions & Answers

please l need past question about economics
Prosper Reply
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Effah
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adepojurafiu
Hi guys can I get Adam Smith's WEALTH OF NATIONS fo sale?
Ukpen
Wat d meaning of management
igwe Reply
disaster management cycle
Gogul Reply
cooperate social responsibility
igwe
Fedric Wilson Taylor also define management as the act of knowing what to do and seeing that it is done in the best and cheapest way
OLANIYI
difference between microeconomics and macroeconomic
Ugyen Reply
microeconomics is the study of individual units, firm and government while macroeconomics is the study of the economic aggregates.
okhiria
The classical theory of full employment
Lovely
what is monopoli power
Adzaho Reply
the situation that prevails when economic forces balance so that economic variables neither increase nor decrease
Bombey
what is equilibrium
Kabir
what are the important of economic to accounting students with references
salihu Reply
Economics is important because it helps people understand how a variety of factors work with and against each other to control how resources such as labor and capital get used, and how inflation, supply, demand, interest rates and other factors determine how much you pay for goods and services.
Muhammad
explain the steps taken by the government in developing rural market?
Azeem Reply
contribution of Adam smith in economics
abel Reply
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Patrick
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AS
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Umarou
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AS
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Amir
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Effah Reply
Pls, I need more explanation on price Elasticity of Supply
Isaac Reply
Is the degree to the degree of responsiveness of a change in quantity supplied of goods to a change in price
Afran
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Humaira
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scor
And what are the resources in land
scor
the proces of using the services of labor and equipmnt together with other in puts to make goods and services availble
Bombey
Okay what is land mobile and land unmobile
scor
Discuss the short-term and long-term balance positions of the firm in the monopoly market?
Rabindranath Reply
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Soumya
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Mitiku
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Mitiku
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Soumya
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Mitiku
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Soumya
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Rabindranath
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Mitiku
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Momoh
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Isaac
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OLANIYI
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OLANIYI
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Lerato
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Umarou
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Humaira
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Liaqat
what is firms
Anteyi Reply
A firm is a business entity which engages in the production of goods and aimed at making profit.
Avuwada
What is autarky in Economics.
Avuwada
what is choice
Tia Reply
So how is the perfect competition different from others
Rev Reply
what is choice
Tia
please what type of commodity is 1.Beaf 2.Suagr 3.Bread
Alfred Reply
1
Naziru
2
Mayor
Researchers demonstrated that the hippocampus functions in memory processing by creating lesions in the hippocampi of rats, which resulted in ________.
Mapo Reply
The formulation of new memories is sometimes called ________, and the process of bringing up old memories is called ________.
Mapo Reply
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Source:  OpenStax, College physics: physics of california. OpenStax CNX. Sep 30, 2013 Download for free at http://legacy.cnx.org/content/col11577/1.1
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