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# Solved: In Example 7.7, we found that the speed of a ISBN: 9781938168000 42

## Solution for problem 19PE Chapter 7

College Physics | 1st Edition

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Problem 19PE

In Example 7.7, we found that the speed of a roller coaster that had descended 20.0 m was only slightly greater when it had an initial speed of 5.00 m/s than when it started from rest. This implies that ΔPE >> KEi . Confirm this statement by taking the ratio of ΔPE to KEi . (Note that mass cancels.)

Example 7.7 Finding the Speed of a Roller Coaster from its Height

(a) What is the final speed of the roller coaster shown in Figure 7.8 if it starts from rest at the top of the 20.0 m hill and work done by frictional forces is negligible? (b) What is its final speed (again assuming negligible friction) if its initial speed is 5.00 m/s?

Step-by-Step Solution:

Solution 19PE

When a body of mass is dropped from a certain height, say , the change in its potential energy is given by . The expression for kinetic energy of an object having mass and velocity is given by . We are required to show that in the example given, the change in potential energy is much greater than the initial kinetic energy.

Step 1 of 3</p>

The roller coaster has descended by 20.0 m.

Let its mass be .

Therefore, the change in potential energy J J Step 2 of 3</p>

The initial speed of the roller coaster is 5.00 m/s.

Therefore, the initial kinetic energy J Step 3 of 3

##### ISBN: 9781938168000

The full step-by-step solution to problem: 19PE from chapter: 7 was answered by , our top Physics solution expert on 07/07/17, 04:39PM. Since the solution to 19PE from 7 chapter was answered, more than 782 students have viewed the full step-by-step answer. This textbook survival guide was created for the textbook: College Physics , edition: 1. College Physics was written by and is associated to the ISBN: 9781938168000. The answer to “In Example 7.7, we found that the speed of a roller coaster that had descended 20.0 m was only slightly greater when it had an initial speed of 5.00 m/s than when it started from rest. This implies that ?PE >> KEi . Confirm this statement by taking the ratio of ?PE to KEi . (Note that mass cancels.)Example 7.7 Finding the Speed of a Roller Coaster from its Height(a) What is the final speed of the roller coaster shown in Figure 7.8 if it starts from rest at the top of the 20.0 m hill and work done by frictional forces is negligible? (b) What is its final speed (again assuming negligible friction) if its initial speed is 5.00 m/s?” is broken down into a number of easy to follow steps, and 121 words. This full solution covers the following key subjects: speed, roller, coaster, its, negligible. This expansive textbook survival guide covers 34 chapters, and 3125 solutions.

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