Learning Check Practice: Concepts in Force and Energy

Vocabulary flashcards covering core physics concepts in forces, kinetic energy, Newton's second law, energy conservation, and athletic performance engineering based on the practice review notes.

Air Resistance (on a Biker)

An opposing horizontal contact force that increases in magnitude with greater headwind speed (such as $30$, $40$, and $50\,\text{km/h}$), causing the biker's forward velocity and kinetic energy to decrease.

Kinetic Energy Loss vs. Headwind Speed

The relationship showing that as headwind velocity increases on a flat road with constant pedaling power (for an $8.3\,\text{kg}$ bike and an $84.0\,\text{kg}$ rider), the biker experiences an increasing percentage loss of kinetic energy, reaching over $90\%$ at $50\,\text{km/h}$.

Drive (Field Hockey)

A technique in field hockey where a player shifts their hands to the very top of the stick and utilizes the full stick length to follow through and strike the ball into the goal.

Stick Mass vs. Swing Speed Effect on Kinetic Energy

Evidence showing that swing speed has a greater effect on ball kinetic energy than stick mass; doubling mass ($400\,\text{g}$ to $800\,\text{g}$) doubles ball speed from $60.5\,\text{mph}$ to $121\,\text{mph}$, whereas doubling swing speed ($2.6\,\text{mph}$ to $5.5\,\text{mph}$) quadruples ball speed from $6.25\,\text{mph}$ to $27.5\,\text{mph}$.

Thermal Energy Dissipation (Ball Impact)

The thermal energy generated when friction with grass and air resistance decrease the overall kinetic energy of a ball, transferring that energy into the random kinetic motion of the ball's microscopic particles so they move faster in place.

Newton's Second Law ($F = ma$ in Load Pulling)

The principle stating that when an applied pulling force ($F$) remains constant, increasing the mass ($m$) of the load causes its acceleration ($a$) and resulting speed to decrease.

Car Mass vs. Speed Relationship

An experimental trend where increasing a car's mass from $400\,\text{kg}$ to $1000\,\text{kg}$ causes pulling speed to drop from $1.9\,\text{m/s}$ to $0.7\,\text{m/s}$, giving a predicted speed of approximately $0.8\text{--}0.86\,\text{m/s}$ for an intermediate mass.

Super Shoes

Advanced competition running shoes (such as the Nike Vaporfly and Nike Alphafly) constructed with a carbon-fiber plate and a thick, resilient foam midsole designed to maximize energy return.

Elastic Potential Energy (Shoe Midsole)

The potential energy stored temporarily in the compressed carbon-fiber plate and foam midsole of a running shoe upon footstrike, which springs back to return kinetic energy to the runner rather than losing it as heat.

Chemical Energy Conservation (Running)

The reduction in a runner's metabolic energy expenditure resulting from footwear that alters muscle contraction mechanics to operate with higher mechanical efficiency.

Technology Doping

The competitive advantage gained by using equipment that artificially enhances athletic performance, which led World Athletics in 2020 to introduce regulations limiting shoe foam stack height to $40\,\text{mm}$ and restricting embedded plate designs.