Astronomy Today (9th Edition)
9th Edition
ISBN: 9780134450278
Author: Eric Chaisson, Steve McMillan
Publisher: PEARSON
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Walking with a steady cadence is very important for covering long distances efficiently. How we place our feet, and how quickly we walk, also depends on the roughness of the surface we are walking upon and on the slope of the surface: we walk carefully on slippery surfaces, and take smaller steps when
hiking up a hill. When we are walking at constant speed in a fixed direction, the horizontal and vertical components of the acceleration of our center of mass must be zero. In addition, the sum of torques about the body's center of mass must also be zero. Consider the situation shown in the figure below.
ALMA
XCM
Х СМ
XCM XCM
XCM
We can model the walking gait of a person as a swing of the front leg and torso about the point where the front foot is planted (shown with a red circle in the figure) and a rotation of the trailing leg about the center of mass (CM) of the person. If each leg of this 78.0 kg person is 85.0 cm long and has a mass
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You are attending a county fair with your friend from your physics class. While walking around the fairgrounds, you discover a new game of skill. A thin rod of mass M = 0.550 kg and length l = 2.80 m hangs from a friction-free pivot at its upper end as shown in the figure.
Pivot
Velcro
M
Incoming
Velcro-covered
ball
m
The front surface of the rod is covered with Velcro. You are to throw a Velcro-covered ball of mass m = 1.20 kg at the rod in an attempt to make it swing backward and rotate all the way across the top. The ball must stick to the rod at all times after striking it. If you cause the rod to rotate over the top
position (that is, rotate 180° opposite of its starting position), you win a stuffed animal. Your friend volunteers to try his luck. He feels that the most torque would be applied to the rod by striking it at its lowest end. While he prepares to aim at the lowest point on the rod, you calculate how fast he must throw
the ball to win the stuffed animal with this…
A hanging weight, with a mass of m₁ = 0.365 kg, is attached by a rope to a block with mass m₂ = 0.835 kg as shown in the figure below. The rope goes over a pulley with a mass of M = 0.350 kg. The pulley can be modeled as a hollow cylinder with an inner radius of R₁ = 0.0200 m, and an outer radius of
R2 = 0.0300 m; the mass of the spokes is negligible. As the weight falls, the block slides on the table, and the coefficient of kinetic friction between the block and the table is μ = 0.250. At the instant shown, the block is moving with a velocity of v; = 0.820 m/s toward the pulley. Assume that the pulley is
free to spin without friction, that the rope does not stretch and does not slip on the pulley, and that the mass of the rope is negligible.
R₂
R₁
Mo
mi
(a) Using energy methods, find the speed of the block (in m/s) after it has moved a distance of 0.700 m away from the initial position shown.
(No Response) m/s
(b) What is the angular speed of the pulley (in rad/s) after the block has…
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