Question

predicting changes in kinetic energy quick check
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 accurately describes his kinetic energy while falling? (1 point)
his kinetic energy increased while his speed increases, then it became constant
his kinetic energy was positive at first, but it decreased to zero when he stopped accelerating
his kinetic energy increased quickly at first, then it increased at a constant rate
his kinetic energy would remain the same for the whole fall as long as he lost no mass

Explanation:

Kinetic energy formula is \(K = \frac{1}{2}mv^{2}\), where \(m\) is mass and \(v\) is velocity. When the skydiver's speed \(v\) increases (from \(20\ m/s\) to \(30\ m/s\) to \(50\ m/s\)), since \(m\) (assuming mass is constant) and \(v\) are in the formula, \(K\) (kinetic energy) increases. When speed becomes constant (\(v = 50\ m/s\)), \(K=\frac{1}{2}m\times(50)^{2}\) (constant as \(m\) and \(v\) are constant).

• Second option: Kinetic energy \(K=\frac{1}{2}mv^{2}\), when he stops accelerating (constant speed \(v

eq0\)), \(K
eq0\).

• Third option: Kinetic energy depends on \(v^{2}\). When speed increases non - linearly (from \(20\) to \(30\) to \(50\)), \(K\) does not increase at a constant rate.
• Fourth option: Since \(v\) changes (from lower values to \(50\ m/s\)), \(K\) changes.

Answer:

His kinetic energy increased while his speed increases, then it became constant.