Question

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.

a) Energy is gained from the thrower; potential energy is converted to kinetic energy during flight.
b) Energy is lost during the throw; potential energy is conserved during flight.
c) Energy is gained from the ground; kinetic energy is converted to potential energy during flight.
d) Energy is lost to the air; kinetic energy is conserved during flight.

Answer 1

Energy is transferred from the thrower's muscles to the javelin, initially in the form of chemical potential energy. The javelin gains kinetic energy as it moves forward and converts potential energy into kinetic energy. On the way back down, the kinetic energy is converted back into potential energy until the javelin hits the ground and comes to a stop.

Step-by-step explanation:

When an athlete picks up a javelin, the energy transfer starts from the thrower's muscles. The thrower applies force to the javelin and does work on it, transferring energy to the javelin. This energy is initially in the form of chemical potential energy stored in the thrower's muscles.

As the thrower launches the javelin, the energy is transferred from the thrower to the javelin. The javelin gains kinetic energy as it moves forward. At the same time, the potential energy of the javelin decreases as it is being propelled forward, converting into kinetic energy. This transformation continues until the javelin reaches the high point of its arc.

On the way back down, the kinetic energy of the javelin is converted back into potential energy. This transformation continues until the javelin hits the ground and comes to a stop. Throughout the flight of the javelin, mechanical energy is also being transformed into heat energy due to air resistance.