College Physics
OER 2016 Edition
ISBN: 9781947172173
Author: OpenStax
Publisher: OpenStax College
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Textbook Question
Chapter 7, Problem 18CQ
Most electrical appliances are rated in watts. Does this rating depend on how long the appliance is on? (When off, it is a zero-watt device.) Explain in terms of the definition of power.
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The de-excitation of a state occurs by competing emission and relaxation processes. If the relaxation mechanisms are very effective:a) the emission of radiation is largeb) the emission of radiation is smallc) the emission occurs at a shorter wavelengthd) the de-excitation occurs only by emission processes
m
C
A block of mass m slides down a ramp of height hand
collides with an identical block that is initially at rest.
The two blocks stick together and travel around a loop of
radius R without losing contact with the track. Point A is
at the top of the loop, point B is at the end of a horizon-
tal diameter, and point C is at the bottom of the loop, as
shown in the figure above. Assume that friction between
the track and blocks is negligible.
(a) The dots below represent the two connected
blocks at points A, B, and C. Draw free-body dia-
grams showing and labeling the forces (not com
ponents) exerted on the blocks at each position.
Draw the relative lengths of all vectors to reflect
the relative magnitude of the forces.
Point A
Point B
Point C
(b) For each of the following, derive an expression in
terms of m, h, R, and fundamental constants.
i. The speed of moving block at the bottom of
the ramp, just before it contacts the stationary
block
ii. The speed of the two blocks immediately…
The velocity of an elevator is given by the graph shown.
Assume the positive direction is upward.
Velocity (m/s)
3.0
2.5
2.0
1.5
1.0
0.5
0
0
5.0
10
15
20
25
Time (s)
(a) Briefly describe the motion of the elevator.
Justify your description with reference to the
graph.
(b) Assume the elevator starts from an initial position
of y = 0 at t=0. Deriving any numerical values
you
need from the graph:
i. Write an equation for the position as a
function of time for the elevator from
t=0 to t = 3.0 seconds.
ii. Write an equation for the position as a
function of time for the elevator from t = 3.0
seconds to t = 19 seconds.
(c) A student of weight mg gets on the elevator
and rides the elevator during the time interval
shown in the graph. Consider the force of con-
tact, F, between the floor and the student. How
Justify your answer with reference to the graph
does F compare to mg at the following times?
and your equations above.
i. = 1.0 s
ii. = 10.0 s
Chapter 7 Solutions
College Physics
Ch. 7 - Give an example of something think of as work in...Ch. 7 - Give an example of a situation in which there is a...Ch. 7 - Describe a situation in which a force is exerted...Ch. 7 - The person in Figure 7.33 does work on the lawn...Ch. 7 - Work done on a system puts energy into it Work...Ch. 7 - When solving for speed in Example 7.4, we kept...Ch. 7 - In Example 7.7, we calculated the final speed of a...Ch. 7 - Does the work you do on a book when you lift it...Ch. 7 - What is a conservative force?Ch. 7 - The force exerted by a diving board is...
Ch. 7 - Define mechanical energy. What is the relationship...Ch. 7 - What is the relationship of potential energy to...Ch. 7 - Consider the following scenario. A car for which...Ch. 7 - Describe the energy transfers and transformations...Ch. 7 - Do devices with efficiencies of less than one...Ch. 7 - List four different forms or types of energy. Give...Ch. 7 - List the energy conversions that occur when riding...Ch. 7 - Most electrical appliances are rated in watts....Ch. 7 - Explain, in terms of the definition of power, why...Ch. 7 - A spark of static electricity, such as that you...Ch. 7 - Explain why it is easier to climb a mountain on a...Ch. 7 - Do you do work on the outside world when you rub...Ch. 7 - Shivering is an involuntary response to lowered...Ch. 7 - Discuss the relative effectiveness of dieting and...Ch. 7 - What is the difference between energy conservation...Ch. 7 - If the efficiency of a coal-fired electrical...Ch. 7 - How much work does a supermarket checkout...Ch. 7 - A 75.0-kg person climbs stairs, gaining 2.50...Ch. 7 - (a) Calculate the work done on a 1500-kg elevator...Ch. 7 - Suppose a car travels 108 km at a speed of 30.0...Ch. 7 - Calculate the work done by an 85.0-kg man who...Ch. 7 - How much work is done by the boy pulling his...Ch. 7 - A shopper pushes a grocery cart 20.0 m at constant...Ch. 7 - Suppose the ski patrol lowers a rescue sled and...Ch. 7 - Compare the kinetic energy of a 20,000-kg truck...Ch. 7 - (a) How fast must a 3000-kg elephant move to have...Ch. 7 - Confirm the value given for the kinetic energy of...Ch. 7 - (a) Calculate the force needed to bring a 950-kg...Ch. 7 - A car's bumper is designed to withstand a 4.0-km/h...Ch. 7 - Boxing gloves are padded to lessen the force of a...Ch. 7 - Using energy considerations, calculate the average...Ch. 7 - A hydroelectric power facility (see Figure 7.38)...Ch. 7 - (a) How much gravitational potential energy...Ch. 7 - Suppose a 350-g kookaburra (a large kingfisher...Ch. 7 - In Example 7.7, we found that the speed of a...Ch. 7 - A 100-g toy car is propelled by a compressed...Ch. 7 - In a downhill ski race, surprisingly, little...Ch. 7 - A 5.00105 -kg subway train is brought to a stop...Ch. 7 - A pogo stick has a spring with a force constant of...Ch. 7 - A 60.0-kg skier with an initial speed of 12.0 m/s...Ch. 7 - (a) How high a hill can a car coast up (engine...Ch. 7 - Using values from Table 7.1, how many DNA...Ch. 7 - Using energy considerations and assuming...Ch. 7 - If the energy in fusion bombs were used to supply...Ch. 7 - (a) Use of hydrogen fusion to supply energy is a...Ch. 7 - The Crab Nebula (see Figure 7.41) pulsar is the...Ch. 7 - Suppose a star 1000 times brighter than our Sun...Ch. 7 - A person in good physical condition can put out...Ch. 7 - What is the cost of operating a 3.00-W electric...Ch. 7 - A large household air conditioner may consume 15.0...Ch. 7 - (a) What is the average power consumption in watts...Ch. 7 - (a) What is the average useful power output of a...Ch. 7 - A 500-kg dragster accelerates from rest to a final...Ch. 7 - (a) How long will it take an 850-kg car with a...Ch. 7 - (a) Find the useful power output of an elevator...Ch. 7 - (a) What is the available energy content, in...Ch. 7 - (a) How long would it takea 1.50105 -kg airplane...Ch. 7 - Calculate the power output needed for a 950-kg car...Ch. 7 - (a) Calculate the power per square meter reaching...Ch. 7 - (a) How long can you rapidly climb stairs...Ch. 7 - (a) What is the power output in watts and...Ch. 7 - Calculate the power output in watts and horsepower...Ch. 7 - (a) What is the efficiency of an out-of-condition...Ch. 7 - Energy that is not utilized for work or heat...Ch. 7 - Using data from Table 7.5, calculate the daily...Ch. 7 - What is the efficiency of a subject on a treadmill...Ch. 7 - Shoveling snow can be extremely taxing because the...Ch. 7 - Very large forces are produced in joints when a...Ch. 7 - Jogging on hard surfaces with insufficiently...Ch. 7 - (a) Calculate the energy in kJ used by a 55.0-kg...Ch. 7 - Kanellos Kanellopoulos flew 119 km from Crete to...Ch. 7 - The swimmer shown in Figure 7.44 exerts an average...Ch. 7 - Mountain climbers carry bottled oxygen when at...Ch. 7 - The awe-inspiring Great Pyramid of Cheops was...Ch. 7 - (a) How long can you play tennis on the 800 kJ...Ch. 7 - Integrated Concepts (a) Calculate the force the...Ch. 7 - Integrated Concepts A 75.0-kg cross-country skier...Ch. 7 - Integrated Concepts The 70.0-kg swimmer in Figure...Ch. 7 - Integrated Concepts A toy gun uses a spring with a...Ch. 7 - Integrated Concepts (a) What force must be...Ch. 7 - Unreasonable Results A car advertisement claims...Ch. 7 - Unreasonable Results Body fat is metabolized,...Ch. 7 - Construct Your Own Problem Consider a person...Ch. 7 - Construct Your Own Problem Consider humans...Ch. 7 - Integrated Concepts A 105-kg basketball player...Ch. 7 - Prob. 1TPCh. 7 - Prob. 2TPCh. 7 - Prob. 3TPCh. 7 - Prob. 4TPCh. 7 - Prob. 5TPCh. 7 - Prob. 6TPCh. 7 - Prob. 7TPCh. 7 - Prob. 8TPCh. 7 - Prob. 9TPCh. 7 - Prob. 10TPCh. 7 - Prob. 11TPCh. 7 - Prob. 12TPCh. 7 - Prob. 13TPCh. 7 - Prob. 14TPCh. 7 - Prob. 15TPCh. 7 - Prob. 16TPCh. 7 - Prob. 17TPCh. 7 - Prob. 18TPCh. 7 - Prob. 19TPCh. 7 - Prob. 20TPCh. 7 - Prob. 21TPCh. 7 - Prob. 22TPCh. 7 - Prob. 23TPCh. 7 - Prob. 24TPCh. 7 - Prob. 25TPCh. 7 - Prob. 26TPCh. 7 - Prob. 27TPCh. 7 - Prob. 28TPCh. 7 - Prob. 29TPCh. 7 - Prob. 30TPCh. 7 - Prob. 31TPCh. 7 - 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- Students are asked to use circular motion to measure the coefficient of static friction between two materials. They have a round turntable with a surface made from one of the materials, for which they can vary the speed of rotation. They also have a small block of mass m made from the sec- ond material. A rough sketch of the apparatus is shown in the figure below. Additionally they have equipment normally found in a physics classroom. Axis m (a) Briefly describe a procedure that would allow you to use this apparatus to calculate the coefficient of static friction, u. (b) Based on your procedure, determine how to analyze the data collected to calculate the coefficient of friction. (c) One group of students collects the following data. r (m) fm (rev/s) 0.050 1.30 0.10 0.88 0.15 0.74 0.20 0.61 0.25 0.58 i. Use the empty spaces in the table as needed to calculate quantities that would allow you to use the slope of a line graph to calculate the coefficient of friction, providing labels with…arrow_forwardPART Aarrow_forwardanswer both questionarrow_forward
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