University Physics Volume 1
18th Edition
ISBN: 9781938168277
Author: William Moebs, Samuel J. Ling, Jeff Sanny
Publisher: OpenStax - Rice University
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Textbook Question
Chapter 12, Problem 70AP
A pencil rests against a corner, as shown below. The sharpened end of the pencil touches a rough horizontal floor. The coefficient of static friction between the eraser and the floor is
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Consider the yo-yo (of mass M and outer radius R) shown in the figure, where the string is being pulled with a force of magnitude F (F < M g) at an angle θ to the horizontal. The radius of the inner axis is r (so that r < R). Assume that the angle ranges from 0 to π/2, and the coefficient of static friction with the ground is very large.
1)Enter an expression for the critical angle (in radians, between 0 and π / 2) at which the yo-yo will remain motionless. Use γ = r / R to simplify your expression.
Consider the yo-yo (of mass M and outer radius R) shown in the figure, where the string is being pulled with a force of magnitude F (F < M g) at an angle θ to the horizontal. The radius of the inner axis is r (so that r < R). Assume that the angle ranges from 0 to π/2, and the coefficient of static friction with the ground is very large.
1)Enter an expression for the critical angle (in radians, between 0 and π / 2) at which the yo-yo will remain motionless. Use γ = r / R to simplify your expression.
2) Calculate this critical angle θc, in degrees, if the yo-yo has an outer radius of 3.6 cm and an inner radius of 0.73 cm.
One end (A) of a thin rod rests on a floor, with coefficient of static friction μs.
The other end (B) of the rod leans against a frictionless wall.
The rod has a length of L and a mass of m. The rod has a uniform density, so the center-of-mass is a distance L/2 from either end.
The rod does not move.
variables only (m, g, L, θ, μs)
a) Draw a free body diagram for the rod clearly showing all forces and where they are applied. Hint: There are four forces!
b) On your diagram, draw and label the line of action and lever arm for the weight force about point A.
c) What is the torque produced by the weight force about point A?
d) Using static equilibrium equations, find the three support forces (two at A, one at B).
e) Given the coefficient of static friction μs, what is the smallest possible angle before the rod starts to move?
Chapter 12 Solutions
University Physics Volume 1
Ch. 12 - Check Your Understanding Solve Example 12.1 by...Ch. 12 - Check your Understanding Explain which one of the...Ch. 12 - Check your Understanding Repeat Example 12.3 using...Ch. 12 - Check Your understanding Repeat ExampIe12.4...Ch. 12 - Check Your Understanding For the situation in...Ch. 12 - Check Your Understanding Solve the problem in...Ch. 12 - Check Your Understanding A 50-kg person stands 1.5...Ch. 12 - Check Your Understanding A 400.0-N sign hangs from...Ch. 12 - Check Your Understanding Find the compressive...Ch. 12 - Check Your Understanding A 2.0-m-long wire...
Ch. 12 - Check Your Understanding If the normal force...Ch. 12 - Check Your Understanding Explain why the concepts...Ch. 12 - What can you say about the velocity of a moving...Ch. 12 - Under what conditions can a rotating body be in...Ch. 12 - What three factors affect the torque created by a...Ch. 12 - Mechanics sometimes put a length of pipe over the...Ch. 12 - If there is only one external force (or toe)...Ch. 12 - If an object is in equilibrium there must be an...Ch. 12 - If an odd number of forces act on an object, the...Ch. 12 - A body moving in a circle with a constant seed is...Ch. 12 - What purpose is served by a long and flexible pole...Ch. 12 - Is it possible to rest a ladder against a rough...Ch. 12 - Show how a spring scale and a simple fulcrum can...Ch. 12 - A painter climbs a ladder. Is the ladder more...Ch. 12 - Note: Unless stated otherwise, the weights of the...Ch. 12 - When a glass bottle full of vinegar warms up, both...Ch. 12 - A thin wire strung between two nails in the wall...Ch. 12 - Review the relationship between stress and strain....Ch. 12 - What type of stress are you applying when you...Ch. 12 - Can compress stress be applied to a rubber band?Ch. 12 - Can Young’s modulus have a negative value? What...Ch. 12 - If a hypothetical material has a negative bulk...Ch. 12 - Discuss how you might measure the bulk modulus of...Ch. 12 - Note: Unless stated othen.ise the weights of the...Ch. 12 - Steel rods are commonly placed in concrete before...Ch. 12 - When tightening a bolt, you push perpendicularly...Ch. 12 - When opening do you push on it perpendicularly...Ch. 12 - Find the magnitude of the tension in each...Ch. 12 - What force must be applied at point P to keep the...Ch. 12 - Is it possible to apply a force at P to keep in...Ch. 12 - Two children push on opposite of a door during...Ch. 12 - A small 1000-kg SUV has a wheel base of 3.0 m. If...Ch. 12 - The uniform seesaw is balanced at its center of...Ch. 12 - A uniform plank rests on a level surface as shown...Ch. 12 - The uniform seesaw shown below is balanced on a...Ch. 12 - In order to get his car out of the mud, a man ties...Ch. 12 - A uniform 40.0-kg scaffold of length 60 m is...Ch. 12 - When the structure shown below is supported at...Ch. 12 - To get up on the roof, a person (mass 70.0 kg)...Ch. 12 - A uniform horizontal strut weighs 400.0 N. One end...Ch. 12 - The forearm shown below is positioned at an angle ...Ch. 12 - The uniform boom shown below weighs 3000N . It is...Ch. 12 - The uniform boom shown below weighs 700N , and the...Ch. 12 - A 12.0m boom, of a crane lifting a 3000kg load is...Ch. 12 - A uniform trapdoor shown below is 1.0m by 1.5m and...Ch. 12 - A 90kg man walks on a sawhorse, as shown below....Ch. 12 - The “lead” in pencils is a graphite composition...Ch. 12 - TV broadcast antennas are the tallest artificial...Ch. 12 - By how much does a 65.0kg mountain climber stretch...Ch. 12 - When water freezes, its volume increases by 9.05 ....Ch. 12 - A farmer making grape juice fills a glass bottle...Ch. 12 - A disk between vertebrae in the spine is subjected...Ch. 12 - A vertebrae is subjected to a shearing force of...Ch. 12 - Calculate the force a piano tuner applies to...Ch. 12 - A 20.0m -tall hollow aluminium flagpole is...Ch. 12 - A copper wire of diameter 1.0cm stretches 1.0 when...Ch. 12 - As an oil well is drilled, each new section of...Ch. 12 - Alarge uniform cylindrical steel rod of density...Ch. 12 - A 90-kg mountain climber bangs from a nylon rope...Ch. 12 - A suspender rod of a suspension bridge is 25.0 m...Ch. 12 - A copper wire is 1.0 m long and it diameter is 1.0...Ch. 12 - A 100-N weight is attached to a free end of a...Ch. 12 - The bulk modulus of a material is 1.01011N/m2 ....Ch. 12 - Normal forces of magnitude 1.0106N are applied...Ch. 12 - During a walk on a rope, a tightrope walker...Ch. 12 - When using a pencil eraser, you exert a vertical...Ch. 12 - Normal forces are applied uniformly over the...Ch. 12 - A uniform rope of cross-sectional area 0.50cm2...Ch. 12 - One end of a vertical metallic wire of length 2.0m...Ch. 12 - An aluminium (=2.7g/cm3) wire is suspended from...Ch. 12 - The coefficient of static friction between the...Ch. 12 - A pencil rests against a corner, as shown below....Ch. 12 - A uniform 4.0m plank weighing 200.0N rests against...Ch. 12 - A 40kg boy jumps from a height of 3.0m , lands on...Ch. 12 - Two thin rods, one made of steel and the other of...Ch. 12 - Two rods, one made of copper and the other of...Ch. 12 - A horizontal force F is applied to a uniform...Ch. 12 - When a motor is set on a pivoted mount seen below,...Ch. 12 - Two wheels A and B with weights w and 2w ,...Ch. 12 - Weights are gradually added to a pan until a wheel...Ch. 12 - In order to lift a shovelful of dirt, a gardener...Ch. 12 - A uniform rod of length 2R and mass M is attached...Ch. 12 - The pole shown below is at a 90.0 bend in a power...
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