Chapter 1-5 Review: Momentum, Work, Energy, and Center of Mass

Flashcards covering key concepts from Chapters 1 through 5: momentum (linear and angular), work, energy, center of mass, gravitational potential energy, energy conversion efficiency, and the role of metabolism in performing work.

Why does applying a force through the center of mass generally not produce torque about the center of mass?

Because the lever arm is zero; torque tau = r × F is zero when the line of action passes through the center of mass.

What explains why a skater speeds up when pulling their arms in during a spin?

Conservation of angular momentum: reducing the moment of inertia increases angular velocity (assuming negligible external torque).

Where does the ground reaction force act relative to the center of mass during a spin or upright stance according to the notes?

Roughly through the center of mass.

What are the two key physical concepts for the energy-based perspective introduced in Chapter 2?

Work and energy.

How is work defined in mechanics?

Work equals force multiplied by displacement in the direction of the force (W = F · d).

If a 100 N force moves an object 10 meters, how much work is done?

1000 joules.

From what source does the body obtain the energy to perform work, as discussed in Chapter 3?

Metabolic conversion of chemical energy from food into muscular work.

Is the conversion from energy to work perfectly efficient?

No; it is not 100% efficient; some energy is lost as heat or other forms.

What is gravitational potential energy?

Potential energy due to an object's height in a gravitational field (height above the ground).

What happens to potential energy and kinetic energy as an object moves under gravity from height to lower height?

Potential energy decreases while kinetic energy increases; energy is exchanged as the object moves downward; conversely, climbing increases potential energy and may reduce kinetic energy.

What is the 'ramp' analogy used to describe in Chapter 4?

A conceptual model for raising the center of mass from a lower height to a higher height through muscle action, like climbing a ramp.

What is the role of metabolism in transforming energy to work?

Metabolic processes convert chemical energy from food into usable mechanical work by muscles.