Abook falls from a desk. which graph best represents the book’s change in potential energy?

The graph C.

Explanation:

The potential energy of the book is maximum when it is on the table; therefore, the graph we are looking for must have maximum potential energy at

Also, as the book falls down, its potential energy is decreasing; therefore, the slope of the graph must be negative.

Finally, as the book lands on the ground, its potential energy becomes zero; therefore, the graph must show potential energy of zero at some time, i.e it must contain a point

Now, looking at the four graphs given, we see that the graph C satisfies all our conditions, and therefore it is the correct choice.

For the sake of completeness, let us look at other choices.

Graph A shows potential energy non linearly increasing—not true for a falling book.

Graph B shows potential energy increasing linearly—not true for a falling book because its potential energy is decreasing.

Graph D shows that potential energy of the book does not change—cannot be true since the book is falling.

answer: the exterior temperature of commercial jet planes as they leave the stratosphere and return to the ground increases steadily.

explanation:

the lower most layer of atmosphere is troposphere which extends from 0 to 12 km above the surface of the earth. the temperature initially decreases as distance is increased from the earth's surface. commercial jets fly in lower part of the stratosphere. the stratosphere extends upto 50 km. the temperature in stratosphere starts rising again due to presence of ozone which traps the uv rays.

thus, when the planes leave the stratosphere and return to the ground, the exterior temperature increases steadily.