Answered: 46. Which of the following pairs of…

46. Which of the following pairs of forces is an action-reaction pair? A. The force a ladder leaning on a smooth wall exerts on the wall and the normal reaction force from the wall.

College Physics

1st Edition

ISBN:9781938168000

Author:Paul Peter Urone, Roger Hinrichs

Publisher:Paul Peter Urone, Roger Hinrichs

Chapter7: Work, Energy, And Energy Resources

Section: Chapter Questions

Problem 12PE: (a) Calculate the force needed to bring a 950-kg car to rest from a speed of 90.0 km/h in a distance...

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(a) Calculate the force needed to bring a 950-kg car to rest from a speed of 90.0 km/h in a distance of 120 m (a fairly typical distance for a non-panic stop). (b) Suppose instead the car hits a concrete abutment at full speed and is brought to a stop in 2.00 m. Calculate the force exerted on the car and compare it with the force found in part (a).
You are part of a team in an engineering class that is working on a scale model of a new design for a life vest. You have been asked to find the mass of a piece of foam that will be used for flotation. Because the piece is too bulky to fit on your balance, you break it into two parts. You measure the mass of the first part as 128.3 0.3 g and the second part as 77.0 0.3 g. a. What are the maximum and minimum values for the total mass you might reasonably report? b. What is the best estimate for the total mass of the foam? Hint: Propagation of uncertainty is described in Appendix A.
Review. A force platform is a tool used to analyze the performance of athletes by measuring the vertical force the athlete exerts on the ground as a function of time. Starting from rest, a 65.0-kg athlete jumps down onto the platform from a height of 0.600 m. While she is in contact with the platform during the time interval 0t 0.800 s, the force she exerts on it is described by the function F = 9 200t 11 500 t2 where F is in newtons and t is in seconds. (a) What impulse did the athlete receive from the platform? (b) With what speed did she reach the platform? (c) With what speed did she leave it? (d) To what height did she jump upon leaving the platform?
You have a new internship, where you are helping to design a new freight yard for the train station in your city. There will be a number of dead-end sidings where single cars can be stored until they are needed. To keep the cars from running off the tracks at the end of the siding, you have designed a combination of two coiled springs as illustrated in Figure P7.41. When a car moves to the right in the figure and strikes the springs, they exert a force to the left on the car to slow it down. Both springs are described by Hookes law and have spring constants k1 = 1 600 N/m and k2 = 3 400 N/m. After the first spring compresses by a distance of d = 30.0 cm, the second spring acts with the first to increase the force to the left on the car in Figure P7.41. When the spring with spring constant k2 compresses by 50.0 cm, the coils of both springs are pressed together, so that the springs can no longer compress. A typical car on the siding has a mass of 6 000 kg. When you present your design to your supervisor, he asks you for the maximum speed that a car can have and be stopped by your device. Figure P7.41
(a) Calculate the magnitude and direction of the force on each foot of the horse in Figure 9.31 (two are on the ground), assuming the center of mass of the horse is midway between the feet. The total mass of the horse and rider is 500kg. (b) What is the minimum coefficient of friction between the hooves and ground? Note that the force exerted by the wall is horizontal.
Professional Application If you dive into water, you reach greater depths if you do a belly flop. Explain this difference in depth using the concept of conservation of energy. Explain this difference in depth using what you have learned in this chapter.
In a head-on, inelastic collision, a 4,000-kg truck going 10 m/s east strikes a 1,000-kg car going 20 m/s west. (a) What is the speed and direction of the wreckage? (b) How much kinetic energy was lost in the Collision?
A bowling ball rolls up a ramp 0.5 m high without slipping to storage. It has an initial velocity of its center of mass of 3.0 m/s. (a) What is its velocity at the top of the ramp? (b) If the ramp is 1 m high does it make it to the top?
A car is stopped for a traffic signal. When the light turns green, the car accelerates, increasing its speed from 0 to 5.20 m/s in 0.832 s. What are the magnitudes of (a) the linear impulse and (b) the average total force experienced by a 70.0-kg passenger in the car during the time the car accelerates?
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A 75.0-kg person is riding in a car moving at 20.0 m/s when the car runs into a bridge abutment (see the following figure). a. Calculate the average force on the person if he is stopped by a padded dashboard that compresses an average of 1.00 cm.b. Calculate the average force on the person if he is stopped by an air bag that compresses an average of 15.0 cm.
Some climbing ropes are designed to noticeably stretch under a load to lessen the forces in a fall. A 10 m length of climbing rope is supporting a climber; this causes the rope to stretch by 60 cm. If the climber is supported by a 20 m length of the same rope, by how much does the rope stretch?A. 30 cm B. 60 cm C. 90 cm D. 120 cm