Chapter 7: Q14 CQ (page 259)

Describe the energy transfers and transformations for a javelin, starting from the point at which an athlete picks up the javelin and ending when the javelin is stuck into the ground after being thrown.

Short Answer

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When an athlete picks up a javelin, the chemical energy stored in his muscles gets converted into potential energy. When the athlete runs, the potential energy gets converted into kinetic energy. When the athlete throws the javelin, all the kinetic energy is transferred into the javelin. Once, the javelin is thrown, it starts losing its kinetic energy due to air resistance and gravitational energy.

Step by step solution

Step 1: Definition of Concepts

Conservation of energy: According to the conservation of energy, energy neither be created nor be destroyed. Only the form of energy can be changed.

Explain the energy transfers and transformations for a javelin

When an athlete picks up a javelin to a certain height, the chemical energy stored in his muscles gets converted into potential energy and stored in the javelin die to increase in height.

After picking up the javelin, when the athlete runs forward, the gravitational potential gets converted into kinetic energy.

When the athlete takes his last step, he shifts his weight on his back foot to increase speed and transfers all kinetic energy into the javelin to throw it away.

Once the javelin is thrown, it starts losing its energy because of air resistance and gravitational force.