In this example we will apply the equations for constant angular acceleration to the simple case of a rotating bicycle wheel. The angular velocity of the rear wheel of a stationary exercise bike is wo = 4.00rad/s at time t = 0, and its angular acceleration is constant and equal to a = 2.15rad/s². A particular spoke coincides with the + axis at time t = 0 (Figure 1). What angle does this spoke make with the + axis at time t = 3.00s? What is the wheel's angular velocity at this time?

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Chapter10: Fixed-axis Rotation
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In this example we will apply the equations for constant
angular acceleration to the simple case of a rotating
bicycle wheel. The angular velocity of the rear wheel of a
stationary exercise bike is wo = 4.00rad/s at time
t = 0, and its angular acceleration is constant and equal
to a = 2.15rad/s². A particular spoke coincides with
the + axis at time t = 0 (Figure 1). What angle does
this spoke make with the + axis at time t = 3.00s?
What is the wheel's angular velocity at this time?
Figure
Att = 0:
1 of 1
0o = 0 for
chosen spoke
SOLUTION
SET UP We take 0 = 0 at the postion where the chosen spoke is horizontal, and we take the counterclockwise rotation to be positive. The
initial conditions are 0o = 0, wo = 4.00rad/s, and a = 2.15rad/s².
SOLVE We can use the equations for constant angular acceleration to find and w at any time. The angle is given as a function of time
Alternatively,
0
Part A Practice Problem:
The wheel has turned through three complete revolutions plus an additional 0.45 rev, or (0.45rev) (2π rad/rev) = 2.83rad = 162°.
Thus, the chosen spoke is at an angle of 162° with the + axis.
The wheel's angular velocity w is given as a fuction of time. At a time t = 3.00s,
wo + at
4.00rad/s+ (2.15rad/s²) (3.00s) = 10.5rad/s
W
=
=
=
=
2
wo² + 2a(0-00)
(4.00rad/s)² + 2(2.15rad/s²) (21.7rad) = 109rad²/s²
10.5rad/s = 1.66rev/s
REFLECT Note the step-by-step similarity between these equations and the kinematic relationships for straight-line motion.
=
0o+wot+at²
0+ (4.00rad/s) (3.00s) + (2.15rad/s²) (3.00s)²
21.7rad = (21.7rad).
1 rev
2π rad
= 3.45rev
=
How much longer will it take before the reference spoke is once again aligned with the + axis?
Express your answer in seconds to three significant figures.
Transcribed Image Text:In this example we will apply the equations for constant angular acceleration to the simple case of a rotating bicycle wheel. The angular velocity of the rear wheel of a stationary exercise bike is wo = 4.00rad/s at time t = 0, and its angular acceleration is constant and equal to a = 2.15rad/s². A particular spoke coincides with the + axis at time t = 0 (Figure 1). What angle does this spoke make with the + axis at time t = 3.00s? What is the wheel's angular velocity at this time? Figure Att = 0: 1 of 1 0o = 0 for chosen spoke SOLUTION SET UP We take 0 = 0 at the postion where the chosen spoke is horizontal, and we take the counterclockwise rotation to be positive. The initial conditions are 0o = 0, wo = 4.00rad/s, and a = 2.15rad/s². SOLVE We can use the equations for constant angular acceleration to find and w at any time. The angle is given as a function of time Alternatively, 0 Part A Practice Problem: The wheel has turned through three complete revolutions plus an additional 0.45 rev, or (0.45rev) (2π rad/rev) = 2.83rad = 162°. Thus, the chosen spoke is at an angle of 162° with the + axis. The wheel's angular velocity w is given as a fuction of time. At a time t = 3.00s, wo + at 4.00rad/s+ (2.15rad/s²) (3.00s) = 10.5rad/s W = = = = 2 wo² + 2a(0-00) (4.00rad/s)² + 2(2.15rad/s²) (21.7rad) = 109rad²/s² 10.5rad/s = 1.66rev/s REFLECT Note the step-by-step similarity between these equations and the kinematic relationships for straight-line motion. = 0o+wot+at² 0+ (4.00rad/s) (3.00s) + (2.15rad/s²) (3.00s)² 21.7rad = (21.7rad). 1 rev 2π rad = 3.45rev = How much longer will it take before the reference spoke is once again aligned with the + axis? Express your answer in seconds to three significant figures.
Part B - Practice Problem:
What will the angular speed of the wheel be at this time?
Express your answer in radians per second to three significant figures.
Transcribed Image Text:Part B - Practice Problem: What will the angular speed of the wheel be at this time? Express your answer in radians per second to three significant figures.
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