56. Go In the sport of skeleton a participant jumps onto a sled (knownas a skeleton) and proceeds to slide down an icy track, belly down andhead first. In the 2010 Winter Olympics, the track had sixteen turns anddropped 126 m in elevation from top to bottom. (a) In the absence ofnonconservative forces, such as friction and air resistance, what wouldbe the speed of a rider at the bottom of the track? Assume that the speedat the beginning of the run is relatively small and can be ignored. (b) Inreality, the gold-medal winner (Canadian Jon Montgomery) reached thebottom in one heat with a speed of 40.5 m/s (about 91 mi/h). How muchwork was done on him and his sled (assuming a total mass of 118 kg) bynonconservative forces during this heat?Frank Gunn/AP/Wide World Photos

In this problem, there will be conservation of mechanical energy in absence of non-conservative…

Answered: 56. Go In the sport of skeleton a…

Principles of Physics: A Calculus-Based Text

5th Edition

ISBN:9781133104261

Author:Raymond A. Serway, John W. Jewett

Publisher:Raymond A. Serway, John W. Jewett

Chapter7: Conservation Of Energy

Section: Chapter Questions

Problem 77P

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A 100 — kg man is skiing across level ground at a speed of 8.0 m/s when he comes to the small slope 1.8 m higher than ground level shown in the following figure. (a) If the skier coasts up the bill, what is his speed when he reaches the top plateau? Assume friction between the snow and skis is negligible. (b) What is his speed when he reaches the upper level if an 80 — N frictional force acts on the skis?
An electric scooter has a battery capable of supplying 120 Wh of energy. If friction forces and other losses account for 60.0% of the energy usage, what altitude change can a rider achieve when driving in hilly ter-rain if the rider and scooter have a combined weight of 890 N?
A 200-g steel ball is tied to a 2.00m “massless” string and hung from the ceiling to make a pendulum, and then, the ball is brought to a position making a 30 angle with the vertical direction and released from rest. Ignoring the effects of the air resistance, find the speed of the ball when the string (a) is vertically down, (b) makes an angle of 20 with the vertical and (c) makes an angle of 10 with the vertical.
A 6.50 102-kg elevator starts from rest and moves upward for 3.00 s with constant acceleration until it reaches its cruising speed, 1.75 m/s. (a) What is the average power of the elevator motor during this period? (b) How does this amount of power compare with its power during an upward trip with constant speed?
A person in good physical condition can put out 100 W of useful power for several hours at a stretch, perhaps by pedaling a mechanism that drives an electric generator. Neglecting any problems of generator efficiency and practical considerations such as resting time: (a) How many people ‘would it take to nm a 4.O0-kW electric clothes dryer? (b) How many people would it take to replace a large electric power plant that generates 800 MW?
Check Your Understanding suppose the radius of the loop-the-loop in Example 7.9 is 15 cm and the toy car starts from rest at a height of 45 cm above the bottom. What is its speed at the top of the loop?
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A block of mass 0.500 kg is pushed against a horizon-tal spring of negligible mass until the spring is compressed a distance x (Fig. P8.65). The force constant of the spring is 450 N/m. When it is released, the block travels along a frictionless, horizontal surface to point , the bottom of a vertical circular track of radius R = 1.00 m, and continues to move up the track. The blocks speed at the bottom of the track is v = 12.0 m/s, and the block experiences an average friction force of 7.00 N while sliding up the track. (a) What is x? (b) If the block were to reach the top of the track, what would be its speed at that point? (c) Does the block actually reach the top of the track, or does it fall off before reaching the top?
An a simple pendulum swings back and forth, the forces acting on the suspended object are (a) the gravitational force, (b) the tension in the supporting cord, and (c) air resistance, (i) Which of these forces, if any, does no work on the pendulum at any time? (ii) Which of these forces does negative work on the pendulum at all Limes during its motion?
A bottle rocket is shot straight up in the air with a speed 30 m/s. if the air resistance is ignores, the bottle would go up to a height of approximately 46 m. however the rocket goes up to only 35 m before returning to the ground. What happened? Explain, giving only a qualitative response.
A particle of mass 4.0 kg is constrained to move along the x -axis under a single force F(x)=cx3 , where c=8.0N/m3 . The particle’s speed at A, where xA=1.0m , is 6.0 m/s. What is its speed at B, where xB=2.0m ?

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