9. Work & Energy

Which two forms of mechanical energy are commonly discussed in introductory physics?

Which of the following is considered an efficient storage of energy?

When comparing the values of gravitational potential energy ($\mathrm{GPE}$) and kinetic energy ($\mathrm{KE}$) for an object in free fall (neglecting air resistance), what do you observe, and which physical law does this illustrate?

In the context of energy transfer in ecosystems, what does the $10\%$ rule refer to, and why is energy lost at each trophic level?

In a mass-spring system oscillating horizontally on a frictionless surface, at which position is the potential energy stored in the spring being converted most rapidly into kinetic energy?

Which of the following correctly expresses the total mechanical energy of an object in terms of its kinetic $K$ and potential $U$ energies?

About 50,000 years ago, a meteor crashed into the earth near present-day Flagstaff, Arizona. Some estimates suggest this meteor had a mass of about 1.4×10⁸ kg and released 1×10¹⁶ J of energy when it slammed into the Earth. Calculate the approximate speed of this meteor before impact.

Which of the following situations describes a person experiencing $\mathrm{weightlessness}$?

A bullet of mass $m$ leaves the muzzle of a gun at a speed of $500m/s$. What is its kinetic energy as it leaves the muzzle?

In physics, energy is defined as the ability to do which of the following?

Under which circumstance is $K$inetic energy transferred from one object to another?

A 150 g particle at x = 0 is moving at 2.00 m/s in the + x - direction. As it moves, it experiences a force given by Fₓ = (0.250 N) sin (x/2.00 m). What is the particle's speed when it reaches x = 3.14 m?

What is the difference between stored energy and usable energy in the context of $\mathrm{kinetic}\mathrm{energy}$ and $\mathrm{potential}\mathrm{energy}$?

Which of the following represents an example of kinetic energy?