Predicting Changes in Kinetic Energy Quick Check
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Question
A skydiver jumps out of a plane and begins to accelerate. His speed increases to 20 m/s, then 30 m/s. His acceleration slows until he reaches a constant speed of 50 m/s. Which statement correctly describes his kinetic energy during this time?(1 point)
Responses
His kinetic energy was positive at first, but it decreased to zero when he stopped accelerating.
His kinetic energy was positive at first, but it decreased to zero when he stopped accelerating.
His kinetic energy would remain the same for the whole fall as long as he lost no mass.
His kinetic energy would remain the same for the whole fall as long as he lost no mass.
His kinetic energy increased while his speed increases, then it became constant.
His kinetic energy increased while his speed increases, then it became constant.
His kinetic energy increased quickly at first, then it increased at a constant rate.
The correct statement is:
His kinetic energy increased while his speed increases, then it became constant.
The correct statement describing the changes in the skydiver's kinetic energy during this time is:
His kinetic energy increased while his speed increased, then it became constant.
To determine the correct statement about the skydiver's kinetic energy, let's understand the relationship between kinetic energy, speed, and acceleration.
Kinetic energy (KE) is given by the equation KE = (1/2)mv^2, where m represents the mass of the object and v represents its velocity (speed). Acceleration (a) is the rate at which the velocity changes.
Based on the information provided, the skydiver starts with an initial speed of 0 m/s and gradually accelerates. It's important to note that kinetic energy depends on the square of the velocity. So, as the skydiver's speed increases from 0 m/s to 20 m/s, then to 30 m/s, his kinetic energy will increase accordingly.
Once the skydiver reaches a constant speed of 50 m/s, it implies there is no more acceleration, i.e., the acceleration becomes zero. At this point, the skydiver's kinetic energy will remain constant because his speed (velocity) is constant. Therefore, the correct statement about the skydiver's kinetic energy is:
His kinetic energy increased while his speed increases, then it became constant.
Option 3: His kinetic energy increased while his speed increases, then it became constant.