Question Detail
Question
Two balls with equal mass are dropped from a height of 2 meters above the floor. They both bounce back up to a maximum height of 1.8 meters above the floor. The first ball is made of steel and is in contact with the floor for 0.04 seconds. The second ball is made of rubber and is in contact with the floor for 0.09 seconds. What is the maximum speed of the steel ball after it bounces off the floor? (acceleration due to gravity, g = 9.81 ms⁻²)
Correct Answer
Option B is the correct answer.
Detailed Explanation
The speed just after the bounce is the speed required to reach a height of 1.8 m. Using v² = u² + 2as, where at the peak v=0, a = -g, and s = 1.8 m. So 0 = u² - 29.811.8. Thus u = √(29.811.8) = √(35.316) = 5.94 m/s.
Hint
The maximum speed after the bounce is the speed it leaves the floor with, which can be found from the height it reaches.