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Chapter 9: Problem 11

A sprinter accelerates out of the starting blocks. Can you consider him as a closed system? Explain.

Short Answer

Expert verified
No, a sprinter accelerating out of the starting blocks cannot be considered a closed system since they are exchanging matter (force) with their environment, specifically the ground, which is outside of the system we are considering.

Step by step solution

01

Understand definition of closed system

A closed system in physics is defined as a type of physical system where matter does not enter or leave, however, energy can still be exchanged with its surroundings.
02

Apply definition to the sprinter scenario

When considering the sprinter, we note that they push against the ground to propel themselves forward. Hence, matter (force) is exchanged between the sprinter and the ground.
03

Conclude

Based on the definition of a closed system and the physical interaction between the sprinter and their surroundings, we can conclude that a sprinter cannot be considered a closed system.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Sprinter Dynamics
In the context of physics, **sprinter dynamics** refers to the forces and motions involved when a sprinter accelerates from a stationary position. At the start of a race, the sprinter exerts force against the ground to initiate movement. This force pushes the sprinter forward, allowing them to accelerate rapidly from the starting blocks.

This process involves the conversion of potential energy (stored in the muscles) into kinetic energy (energy of motion). Key elements include:
  • Muscle contraction: The sprinter's muscles contract, generating force.
  • Ground reaction: The ground provides an equal and opposite reaction force, based on Newton鈥檚 third law of motion.
  • Acceleration: This reaction force allows the sprinter to accelerate along the track.
Understanding sprinter dynamics helps in appreciating how athletes optimize their start to improve performance and achieve faster times.
System Interaction
**System interaction** is a core concept in understanding how a sprinter interacts with their environment. In physics, the focus is on the exchanges of forces and energy which occur between different components of a scenario. For the sprinter, these interactions are crucial to how they gain momentum and speed.

Key interactions involve:
  • The sprinter and the starting blocks: As the sprinter pushes off, there is a significant force exchange which helps in early acceleration.
  • The sprinter's feet and the track: Continuous interaction occurs as the foot strikes and pushes against the ground, propelling the sprinter forward.
  • The sprinter's body and air: Air resistance acts against the sprinter, impacting their speed. Sprinters often train to minimize this effect through improved aerodynamic techniques.
Through these interactions, sprinters manipulate the forces in play to maximize their start and maintain speed throughout a race.
Energy Exchange
**Energy exchange** in the context of a sprinter involves the transformation and movement of energy within and outside the sprinter's body. This concept is integral to understanding why a sprinter cannot be considered a closed system.

Here are the main forms of energy involved:
  • Chemical energy: The sprinter's muscles use chemical energy stored in the body from food.
  • Kinetic energy: As the muscles contract, this chemical energy is converted into kinetic energy, moving the sprinter.
  • Thermal energy: Some energy is also converted into heat, which is why sprinters often warm up before races to optimize muscle efficiency.
During a race, energy is also exchanged with the environment. The sprinter transfers energy to the ground as they push off, and to the air via resistance. This constant exchange underscores why the sprinter is not a closed system, as energy flows idly in and out from the surroundings.

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