# A 26 kg bear slides, from rest, 11 m down a lodgepole pine tree, moving with a speed of 4.1 m/s...

## Question:

A 26 kg bear slides, from rest, 11 m down a lodgepole pine tree, moving with a speed of 4.1 m/s just before hitting the ground.

a. What change occurs in the gravitational potential energy of the bear-Earth system during the slide?

b. What is the kinetic energy of the bear just before hitting the ground?

c. What is the average frictional force that acts on the sliding bear?

## Work-Energy Theorem:

The theorem states that the kinetic energy gained by an object is a result of the net-work done on it.

When a body of mass *m* is at a height *h* above the ground, it possesses potential energy given by *mgh* where *g* is the gravitational acceleration value. When such a body falls, it loses potential energy and gains kinetic energy **Ek** given by {eq}E_k = \frac{1}{2}mv^2
{/eq}, where **v** is the velocity gain. However, practically, some work is done against friction and so the value of **v** and hence the kinetic energy **Ek**is less than the expected value.

## Answer and Explanation:

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View this answer**Part a**

The gravitational potential energy **Ep** of the mass-Earth system is given by *mgh* where *m* is the mass of the object, *g* is the gravitational...

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Chapter 8 / Lesson 7Work and energy are closely related in physics. In this lesson, you'll learn what that relationship is as well as how we can apply it to various situations.