15. FIGURE Q4.15 shows a pendulum at one end point of its arc.
a. At this point, is positive, negative, or zero? Explain.
b. At this point, is positive, negative, or zero? Explain.
Part (a) At the end point the angular velocity is zero.
Part (b) At the end point angular acceleration is negative.
The relation between tangential velocity and angular velocity is
Here is tangential velocity and is angular velocity.
When the pendulum is at the end point of the arc then is zero because at the end point the velocity is zero.
(b) At the end point angular acceleration ' ' is negative because angular velocity changes from positive value to zero.
A rubber ball is dropped onto a ramp that is tilted at 20°, as shown in FIGURE P4.59. A bouncing ball obeys the “law of reflection,” which says that the ball leaves the surface at the same angle it approached the surface. The ball’s next bounce is 3.0 m to the right of its first bounce. What is the ball’s rebound speed on its first bounce?
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