A) The average acceleration formula can be used to determine the jumper's speed when the bungee cord starts to stretch:
Since the jumper falls for 1.3 s before the bungee cord begins to stretch, the time can be taken as 1.3 s. The average acceleration is given as 4 m/s². We can rearrange the formula to solve for the change in velocity:
Substituting the values:
Thus, the change in velocity is .
Therefore, the speed of the jumper when the bungee cord begins to stretch is 5.2 m/s.
B) To determine how far below the diving platform the jumper is at that moment, we can use the equation of motion for linear motion:
At the moment the bungee cord begins to stretch, the final velocity is 0 m/s (as the jumper momentarily stops before rebounding), the initial velocity is the speed of the jumper when the bungee cord begins to stretch (5.2 m/s), the acceleration is the average acceleration (4 m/s²), and we want to find the distance.
Rearranging the equation, we have:
Substituting the values:
Thus, the distance below the diving platform is m.
Note that the negative sign indicates that the jumper is below the diving platform.
Therefore, the jumper is 6.76 m below the diving platform at that moment.
C) To determine how long it takes for the jumper to reach the low point of the drop after the bungee cord begins to stretch, we can use the equation of motion:
At the low point of the drop, the final velocity is 0 m/s (as the jumper momentarily stops before rebounding), the initial velocity is the speed of the jumper when the bungee cord begins to stretch (5.2 m/s), the acceleration is the acceleration due to gravity (which is approximately -9.8 m/s² since it acts in the opposite direction of the upward motion), and we want to find the time.
Rearranging the equation, we have:
Substituting the values:
Thus, the time it takes for the jumper to reach the low point of the drop after the bungee cord begins to stretch is s.
Therefore, it takes approximately 0.5316 s for the jumper to reach the low point of the drop after the bungee cord begins to stretch.
D) To determine how far below the diving platform the jumper is at the instant the speed is zero, we can again use the equation of motion:
At the instant the speed is zero, the final velocity is 0 m/s, the initial velocity is the speed of the jumper when the bungee cord begins to stretch (5.2 m/s), the acceleration is the acceleration due to gravity (-9.8 m/s²), and we want to find the distance.
Rearranging the equation, we have:
Substituting the values:
Thus, the distance below the diving platform is m.
Therefore, the jumper is approximately 1.3567 m below the diving platform at the instant the speed is zero.