A toy airplane hangs from the ceiling at the bottom end of a string. Yon turn the airplane many times to wind up the string clockwise and release it. The airplane starts to spin counterclockwise, slowly at first and then faster and faster. Take counterclockwise as the positive sense and assume friction is negligible. When the string is entirely unwound, the airplane has its maximum rate of rotation, ( i ) At this moment, is its angular acceleration (a) positive. (b) negative, or (c) zero? ( ii ) The airplane continues to spin, winding the string counterclockwise as it slows clown. At the moment it momentarily stops, is its angular acceleration (a) positive, (b) negative, or (c) zero?
A toy airplane hangs from the ceiling at the bottom end of a string. Yon turn the airplane many times to wind up the string clockwise and release it. The airplane starts to spin counterclockwise, slowly at first and then faster and faster. Take counterclockwise as the positive sense and assume friction is negligible. When the string is entirely unwound, the airplane has its maximum rate of rotation, ( i ) At this moment, is its angular acceleration (a) positive. (b) negative, or (c) zero? ( ii ) The airplane continues to spin, winding the string counterclockwise as it slows clown. At the moment it momentarily stops, is its angular acceleration (a) positive, (b) negative, or (c) zero?
Solution Summary: The author determines the nature of angular acceleration of the airplane at maximum rate of rotation.
A toy airplane hangs from the ceiling at the bottom end of a string. Yon turn the airplane many times to wind up the string clockwise and release it. The airplane starts to spin counterclockwise, slowly at first and then faster and faster. Take counterclockwise as the positive sense and assume friction is negligible. When the string is entirely unwound, the airplane has its maximum rate of rotation, (i) At this moment, is its angular acceleration (a) positive. (b) negative, or (c) zero? (ii) The airplane continues to spin, winding the string counterclockwise as it slows clown. At the moment it momentarily stops, is its angular acceleration (a) positive, (b) negative, or (c) zero?
Definition Definition Rate of change of angular velocity. Angular acceleration indicates how fast the angular velocity changes over time. It is a vector quantity and has both magnitude and direction. Magnitude is represented by the length of the vector and direction is represented by the right-hand thumb rule. An angular acceleration vector will be always perpendicular to the plane of rotation. Angular acceleration is generally denoted by the Greek letter α and its SI unit is rad/s 2 .
Point charges of 6.50 μC and -2.50 μC are placed 0.300 m apart. (Assume the negative charge is located to the right of the positive charge. Include the sign of the value in your answers.)
(a) Where can a third charge be placed so that the net force on it is zero?
0.49
m to the right of the -2.50 μC charge
(b) What if both charges are positive?
0.49
xm to the right of the 2.50 μC charge
Find the electric field at the location of q, in the figure below, given that q₁ =9c9d = +4.60 nC, q = -1.00 nC, and the square is 20.0 cm on a side. (The +x axis is directed to the right.)
magnitude
direction
2500
x
What symmetries can you take advantage of? What charges are the same magnitude and the same distance away? N/C
226
×
How does charge sign affect the direction of the electric field? counterclockwise from the +x-axis
9a
9b
%
9
9d
Chapter 10 Solutions
Physics for Scientists and Engineers, Technology Update (No access codes included)
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