Chapter 6: Q.11 (page 154)
FIGURE EXshows the force acting on a object as it moves along the x-axis. The object is at rest at the origin atWhat are its acceleration and velocity at ?

Short Answer
At ,
(a) Acceleration =,
(b) Velocity =.
Chapter 6: Q.11 (page 154)
FIGURE EXshows the force acting on a object as it moves along the x-axis. The object is at rest at the origin atWhat are its acceleration and velocity at ?

At ,
(a) Acceleration =,
(b) Velocity =.
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Large objects have inertia and tend to keep moving-Newton's BI0 first law. Life is very different for small microorganisms that swim through water. For them, drag forces are so large that they instantly stop, without coasting, if they cease their swimming motion. To swim at constant speed, they must exert a constant propulsion force by rotating corkscrew-like flagella or beating hair-like cilia. The quadratic model of drag of Equation fails for very small particles. Instead, a small object moving in liquid experiences a linear drag force, , the direction opposite the motion), where is a constant. For a sphere of radius , the drag constant can be shown to be , where is the viscosity of the liquid. Water at has viscosity .
a. A paramecium is about long. If it's modeled as a sphere, how much propulsion force must it exert to swim at a typical speed of ? How about the propulsion force of a --diameter . coli bacterium swimming at ?
b. The propulsion forces are very small, but so are the organisms. To judge whether the propulsion force is large or small relative to the organism, compute the acceleration that the propulsion force could give each organism if there were no drag. The density of both organisms is the same as that of water, .
Very small objects, such as dust particles, experience a linear drag force,(bv, direction opposite the motion), where is a constant. That is, the quadratic model of drag of Equation fails for very small particles. For a sphere of radius , the drag constant can be shown to be , where is the viscosity of the gas.
a. Find an expression for the terminal speedof a spherical particle of radius and mass falling through a gas of viscosity .
b. Suppose a gust of wind has carrieda -diameter dust particle to a height of . If the wind suddenly stops, how long will it take the dust particle to settle back to the ground? Dust has a density ofrole="math" localid="1647776411884" the viscosity ofair is , and you can assume that the falling dust particle reaches terminal speed almost instantly.
It shows an accelerometer, a device for measuring the horizontal acceleration of cars and airplanes. A ball is free to roll on a parabolic rack described by the equation, where both and are in meters. A scale along the bottom is used to measure the ball's horizontal position.
a. Find an expression that allows you to use a measured position to compute the acceleration. (For example, is a possible expression.)
b. What is the acceleration if

You and your friend Peter are putting new shingles on a roof pitched at 25°. You’re sitting on the very top of the roof when Peter, who is at the edge of the roof directly below you, 5.0 m away, asks you for the box of nails. Rather than carry the 2.5 kg box of nails down to Peter, you decide to give the box a push and have it slide down to him. If the coefficient of kinetic friction between the box and the roof is 0.55, with what speed should you push the box to have it gently come to rest right at the edge of the roof?
The three ropes inare tied to a small, very light ring. Two of the ropes are anchored to walls at right angles, and the third rope pulls as shown. What are and , the magnitudes of the tension forces in the first two ropes?

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