B.2.1.4 Work, energy, and power in force application (HL) Notes

Work and power

1. Work is only done if displacement occurs (e.g., holding a weight without moving it does no work).
2. If force and displacement are in the same direction, work is positive (e.g., lifting a weight).
3. If force and displacement are in opposite directions, work is negative (e.g., lowering a weight).
4. No work is done if the force is perpendicular to movement (e.g., carrying a tray while walking forward).
5. Work is calculated using the formula:

W = F x D

1. W = Work (Joules, J)
2. F = Force applied (Newtons, N)
3. d = Displacement of the object (meters, m)

1. Power combines:
   1. Force application
   2. Velocity of movement
   3. Timing and technique
2. Key Factors Affecting Power:
   1. Force applied: More force increases power output.
   2. Speed of movement: Faster execution of a movement increases power.
3. Power in Sport:
   1. Explosive movements (high power output): Sprinting, weightlifting, and jumping.
   2. Sustained power (lower but continuous output): Distance running, swimming, and cycling.
   3. Power is crucial in sports that require bursts of strength, such as shot put and high jump.

Optimizing Power Output

1. Through technique:
   1. Proper biomechanics
   2. Efficient movement patterns
   3. Optimal force application
   4. Minimizing energy waste
2. Through equipment:
   1. Proper sizing and fit
   2. Material selection
   3. Design efficiency
   4. Regular maintenance

Practical Applications

1. In explosive movements:
   1. Jumping (vertical power)
   2. Throwing (rotational power)
   3. Sprinting (horizontal power)
2. In sustained activities:
   1. Cycling (continuous power)
   2. Swimming (rhythmic power)
   3. Running (endurance power)

Energy

Types of Mechanical Energy:

1. Kinetic Energy (Energy of Motion):
   1. Depends on mass and speed.
   2. Increases with higher velocity (e.g., a fast-moving soccer ball has more kinetic energy than a slow one).

2. Potential Energy (Stored Energy):

1. Exists due to an object’s position or condition.
2. A higher position increases stored energy (e.g., a diver on a high platform has more potential energy than one on a low board).

3. Elastic Potential Energy:

1. Stored in objects that can stretch or compress, such as springs, rubber bands, or muscle tendons.
2. Important in movements like jumping, where energy is stored and released.

4. Energy Transformation in Sport:

1. A pole vaulter converts potential energy into kinetic energy during takeoff.
2. A basketball player jumps by converting stored energy in leg muscles into motion energy.

The relationship between work, energy, and power

1. Work is needed to change an object’s energy.
2. Energy allows an athlete to perform work.
3. Power determines how quickly an athlete can use energy to perform work.

Sport-Specific Examples:

1. A cyclist generates power by continuously applying force to the pedals.
2. A soccer player uses kinetic energy to strike a ball, transferring energy to it.
3. A gymnast performing a flip converts stored energy into movement energy.

Energy transformations in work

1. Energy is the capacity to do work, and it exists in various forms:
2. Kinetic Energy: Energy of motion (e.g., a sprinter accelerating).
3. Potential Energy: Stored energy due to position (e.g., a diver at the top of a platform).
4. Chemical Energy: Stored in muscles and converted to mechanical energy during movement.