PHYS125 - Physics of Sports Final

Essential questions + answers

What is physics?

Physics is the study of matter, energy, motion, and the forces that govern the universe.

How is physics different from biology and chemistry?

Physics studies fundamental laws of nature; chemistry focuses on interactions of substances; biology studies living organisms.

How is engineering different from physics?

Physics explains natural laws; engineering applies those laws to design and solve practical problems.

Why are units necessary?

Units provide a standard way to measure and compare quantities.

What are SI units?

The International System of Units based on meters, kilograms, and seconds (MKS system).

What are common SI base units?

Length = meter (m), mass = kilogram (kg), time = second (s).

Why estimate physical quantities?

Estimation helps when exact measurements are unnecessary or impossible.

What is an example of estimation in sports?

Estimating the speed of a baseball pitch or distance of a long jump.

What is center of mass?

The point where an object’s mass is effectively concentrated.

Why is center of mass important for motion?

An object moves as if all external forces act on its center of mass.

Why is center of mass important for balance?

Stability increases when the center of mass stays above the base of support.

How do athletes improve balance?

By lowering their center of mass and widening their stance.

What are sports examples of center of mass?

High jump, gymnastics, wrestling, skiing, football blocking.

How does a high jumper use center of mass?

By arching the body so the center of mass passes below the bar.

What quantities describe motion?

Position, displacement, speed, velocity, and acceleration.

What is the difference between speed and velocity?

Speed is magnitude only; velocity includes direction.

What are the types of motion?

Linear, rotational, and projectile motion.

What is average speed?

Total distance divided by total time.

What is instantaneous speed?

Speed at a specific moment in time.

Why distinguish average vs instantaneous speed in sports?

Athletes may have higher peak speed but lower average speed.

What is an example of average vs instantaneous speed?

Sprinters compare top speed vs race-average speed.

What is acceleration?

The rate of change of velocity.

What is the formula for acceleration?

a = Δv / Δt

What is the difference between being fast and being quick?

Fast means high speed; quick means rapid acceleration or direction change.

What causes motion to change?

A net force.

What are three ways velocity can change?

Speed up, slow down, or change direction.

What does constant velocity mean?

Constant speed and constant direction.

What are sports examples of acceleration?

Sprint starts, cutting in football, braking in skiing.

What acceleration acts on vertically moving objects near Earth?

Gravity, g = 9.8 m/s² downward.

What happens to upward velocity during flight?

Gravity slows it until velocity becomes zero at maximum height.

What is the formula for maximum height?

h = vi² / 2g

What is the formula for time to peak?

t = vi / g

What are examples of vertical motion in sports?

Basketball jumps, diving, volleyball spikes.

When does constant acceleration occur?

When gravity is the only force acting.

When does non-constant acceleration occur?

When forces like drag vary during motion.

What is Newton’s First Law?

Objects remain at rest or constant velocity unless acted on by a net force.

What is Newton’s Second Law?

F = ma

What is Newton’s Third Law?

Every action force has an equal and opposite reaction force.

What is the difference between mass and weight?

Mass is amount of matter; weight is gravitational force.

What is the formula for weight?

W = mg

What are the most important sports forces?

Gravity, friction, drag, normal force, applied force.

What is a free-body diagram?

A sketch showing all forces acting on an object.

What is friction?

A force opposing motion between surfaces.

What is the difference between static and kinetic friction?

Static friction acts before movement; kinetic friction acts during movement.

Which is usually greater: static or kinetic friction?

Static friction.

Why is friction important in sports?

It provides traction and control.

What are examples of friction in sports?

Cleats gripping turf, basketball shoe traction, curling stones.

How does friction help athletes accelerate?

Ground pushes back on the athlete due to friction.

What force is needed for circular motion?

Centripetal force.

What direction does centripetal force act?

Toward the center of the circle.

What is the formula for centripetal force?

Fc = mv² / r

What are sports examples of circular motion?

Hammer throw, cycling turns, running curves.

What happens if centripetal force disappears?

The object moves tangentially.

What is projectile motion?

Motion under gravity alone after launch.

What is horizontal acceleration in ideal projectile motion?

Zero.

What is vertical acceleration in projectile motion?

-9.8 m/s²

What shape is projectile motion?

Parabolic.

What determines projectile range?

Initial speed, launch angle, and height.

What is the ideal launch angle for maximum range?

45° without air resistance.

What are sports examples of projectiles?

Football punts, shot put, basketball shots.

What are examples of humans as projectiles?

Long jump, high jump, dunking.

What is buoyant force?

Upward force exerted by a fluid on an object.

What causes buoyancy?

Pressure differences in fluids.

What is Archimedes’ Principle?

Buoyant force equals the weight of displaced fluid.

What sports involve buoyancy?

Swimming, diving, water polo.

Why do swimmers float better in salt water?

Salt water is denser.

What is drag force?

Air or water resistance opposing motion.

What factors affect drag?

Speed, shape, area, and fluid density.

How do athletes reduce drag?

By streamlining body position and equipment.

What sports are strongly affected by drag?

Cycling, swimming, skiing, baseball.

What is terminal velocity?

Speed where drag balances weight.

What is the Magnus effect?

A spinning object creates pressure differences causing curved motion.

What causes Magnus force?

Spin interacting with airflow.

What are examples of the Magnus effect in sports?

Curveballs, soccer bends, tennis topspin.

What does topspin do?

Makes the ball drop faster.

What does backspin do?

Keeps the ball in the air longer.

What is lift?

Upward force caused by pressure differences in airflow.

How is lift created?

Faster airflow lowers pressure.

How does lift help a discus throw?

Spin stabilizes and increases flight distance.

How does air density affect sports?

Lower density reduces drag and increases travel distance.

Why do baseballs travel farther at high altitude?

Reduced air resistance.

What is the formula for momentum?

p = mv

What is impulse?

Force applied over time.

What is the formula for impulse?

J = FΔt

What is the impulse-momentum theorem?

Impulse equals change in momentum.

What is an elastic collision?

A collision where momentum and kinetic energy are conserved.

What is an inelastic collision?

A collision where momentum is conserved but kinetic energy is lost.

What does the coefficient of restitution measure?

Bounciness of a collision.

What is torque?

The rotational effect of a force.

What is the formula for torque?

τ = rFsinθ

What is the formula for kinetic energy?

KE = 1/2 mv²

What is the formula for gravitational potential energy?

PE = mgh

What is the formula for elastic potential energy?

PE = 1/2 kx²

What is efficiency?

Useful output energy divided by input energy.

What is the Law of Conservation of Energy?

Energy cannot be created or destroyed.

What is Hooke’s Law?

F = -kx

What is chemical energy in sports?

Energy stored in ATP and food molecules.

What is the archer’s paradox?

The arrow flexes around the bow during launch.

What is power?

The rate of doing work.

What is the formula for power?

P = W / t