SSM A massless rigid rod of length L has a ball of mass m attached to one end (Fig. 8-68). The other end is pivoted in such a way that the ball will move in a vertical circle. First, assume that there is no friction at the pivot. The system is launched downward from the horizontal position A with initial speed v 0 . The ball just barely reaches point D and then stops. (a) Derive an expression for v 0 in terms of L, m , and g. (b) What is the tension in the rod when the ball passes through B ? (c) A little grit is placed on the pivot to increase the friction there. Then the ball just barely reaches C when launched from A with the same speed as before. What is the decrease in the mechanical energy during this motion? (d) What is the decrease in the mechanical energy by the time the ball finally comes to rest at B after several oscillations? Figure 8-68 Problem 87.
SSM A massless rigid rod of length L has a ball of mass m attached to one end (Fig. 8-68). The other end is pivoted in such a way that the ball will move in a vertical circle. First, assume that there is no friction at the pivot. The system is launched downward from the horizontal position A with initial speed v 0 . The ball just barely reaches point D and then stops. (a) Derive an expression for v 0 in terms of L, m , and g. (b) What is the tension in the rod when the ball passes through B ? (c) A little grit is placed on the pivot to increase the friction there. Then the ball just barely reaches C when launched from A with the same speed as before. What is the decrease in the mechanical energy during this motion? (d) What is the decrease in the mechanical energy by the time the ball finally comes to rest at B after several oscillations? Figure 8-68 Problem 87.
SSM A massless rigid rod of length L has a ball of mass m attached to one end (Fig. 8-68). The other end is pivoted in such a way that the ball will move in a vertical circle. First, assume that there is no friction at the pivot. The system is launched downward from the horizontal position A with initial speed v0. The ball just barely reaches point D and then stops. (a) Derive an expression for v0 in terms of L, m, and g. (b) What is the tension in the rod when the ball passes through B? (c) A little grit is placed on the pivot to increase the friction there. Then the ball just barely reaches C when launched from A with the same speed as before. What is the decrease in the mechanical energy during this motion? (d) What is the decrease in the mechanical energy by the time the ball finally comes to rest at B after several oscillations?
Critical damping is the case where the mass never actually crosses over equilibrium position, but reaches equilibrium as fast as possible. Experiment with changing c to find the critical damping constant. Use the same initial conditions as in the last problem. Zoom in a bit to make sure you don't allow any oscillations to take place - even small ones.
NASA's KC-135 Reduced Gravity Research aircraft, affectionately known as the "Vomit Comet," is used in training astronauts and testing equipment for microgravity environments. During a typical mission, the aircraft makes approximately 30 to 40 parabolic arcs. During each arc, the aircraft and objects inside it are in free-fall, and
passengers float freely in apparent "weightlessness."
The figure below shows the altitude of the aircraft during a typical mission. It climbs from 24,000 ft to 30,850 ft, where it begins a parabolic arc with a velocity of 155 m/s at 45.0° nose-high and exits with velocity 155 m/s at 45.0° nose-low.
31 000
45° nose high
45° nose low
24 000
Zero g
65
Maneuver time (s)
(a) What is the aircraft's speed (in m/s) at the top of the parabolic arc?
110.0
m/s
(b) What is the aircraft's altitude (in ft) at the top of the parabolic arc?
2.04e+04
What is the initial height at the start of the parabolic arc? What is the initial velocity at this point? What is the final…
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