Physics 1: Energy, Kinetic Energy, and Work

Comprehensive practice flashcards covering kinetic energy, work, mechanical energy transformations, and problem-solving examples from Physics 1 lecture notes.

According to the Law of Conservation of Energy (Energilagen), how does energy behave?

Energy can neither be created nor destroyed; it can only be converted or transferred.

What units of measurement for energy are listed in the introductory lecture?

Joule ($\text{J}$), Newton-meter ($\text{Nm}$), Calorie ($\text{cal}$), and Kilowatt-hour ($\text{kWh}$).

What two primary forms constitute mechanical energy in the lecture?

Potential energy (lägesenergi) and kinetic energy (rörelseenergi).

How is work (arbete) defined in relation to energy?

Work is defined as the transformation or conversion of energy ($\text{Arbete} = \text{omvandlingen}$).

What is the formula for kinetic energy ($E_k$), and what units do the variables use?

$E_k = \frac{m \cdot v^2}{2}$, where $m$ is mass in kilograms ($\text{kg}$), $v$ is velocity in meters per second ($\text{m/s}$), and $E_k$ is kinetic energy in Joules ($\text{J}$).

In the mini-lab, what is the kinetic energy of a golf ball with a mass of approximately $45\,\text{g}$ rolling at $1.2\,\text{m/s}$?

Approximately $0.032\,\text{J}$ ($32\,\text{mJ}$), calculated as $E_k = \frac{0.045\,\text{kg} \times (1.2\,\text{m/s})^2}{2} \approx 0.0324\,\text{J}$.

If a tennis ball has a mass of $56\,\text{g}$ and a kinetic energy of $0.69\,\text{J}$, what is its speed?

Approximately $5.0\,\text{m/s}$ ($\approx 4.96416\,\text{m/s}$), calculated from $v = \sqrt{\frac{2 \times 0.69\,\text{J}}{0.056\,\text{kg}}}$.

For Kenny falling from a height of $8848\,\text{m}$ with a mass of $30\,\text{kg}$, what is the initial potential energy ($g = 9.82\,\text{m/s}^2$)?

$E_p = 30\,\text{kg} \times 9.82\,\text{m/s}^2 \times 8848\,\text{m} = 2\,606\,620.8\,\text{J}$.

Assuming all of Kenny's initial potential energy ($2\,606\,620.8\,\text{J}$) converts to kinetic energy upon landing ($m = 30\,\text{kg}$), what is his calculated landing speed?

Approximately $420\,\text{m/s}$ ($\approx 416.863\,\text{m/s}$), calculated using $v = \sqrt{\frac{2 \times 2\,606\,620.8\,\text{J}}{30\,\text{kg}}}$.

How does Kenny's calculated landing speed of $\approx 420\,\text{m/s}$ compare to the speed of sound given in the notes?

It is faster than the speed of sound, which is noted as $v_{\text{ljud}} \sim 340\,\text{m/s}$.

What website and simulation are referenced for kinetic energy visualization?

phet.colorado.edu (energy skate park).

What is the formula and standard units for mechanical work?

$W = F \cdot s$, where $W$ is work in Joules ($\text{J}$) or Newton-meters ($\text{Nm}$), $F$ is force in Newtons ($\text{N}$), and $s$ is displacement in meters ($\text{m}$).

What condition must be met regarding force and displacement for work to occur?

The force and the displacement must be in the same direction, and the object must actually be moved/affected.

If a person applies a force of $500\,\text{N}$ on a stone for $10\,\text{min}$ but the stone does not move, how much work is performed on the stone?

$0\,\text{J}$, because no displacement occurred ($s = 0\,\text{m}$).

How much work is required to lift a $65.0\,\text{kg}$ stone vertically onto a bench with a height of $72\,\text{cm}$ ($g = 9.82\,\text{m/s}^2$)?

Approximately $460\,\text{J}$ ($459.576\,\text{J}$), calculated as $F_g = 65.0\,\text{kg} \times 9.82\,\text{m/s}^2 \approx 638.3\,\text{N}$ and $W = 638.3\,\text{N} \times 0.72\,\text{m}$.

How much work is needed to roll a stone up a $1.44\,\text{m}$ long ramp at a $30^\circ$ incline with a force of $319\,\text{N}$?

Approximately $459\,\text{J}$ ($459.36\,\text{J}$), calculated as $W = 319\,\text{N} \times 1.44\,\text{m}$.

If a bicycle has an initial kinetic energy of $1.6\,\text{kJ}$ and stops with a braking force of $300\,\text{N}$, what is the braking distance?

Approximately $5.3\,\text{m}$ ($\approx 5.333\,\text{m}$), calculated using $W = F \cdot s \Rightarrow 1600\,\text{J} = 300\,\text{N} \times s$.

When a cyclist applies the brakes to stop, what form of energy is the kinetic energy converted into?

Thermal energy / heat (värmeenergi).