Permalink Submitted by Anonymous on April 24, 2014

In what sense is the ball moving at 10 meters per second? "The speed of the ball relative to the ground is actually (10^2+8^2)1/2=12.8 metres per second," and if "it takes 0.4 seconds to travel the 5 metres between the players," then relative to the players the speed is 12.5 meters per second (5/0.4). Also, if the time it takes the ball to reach the other player is 0.4 seconds than its speed relative to the ground is (√(5^2 + (0.4(8))^2))/0.4 = 14.84. However, if it takes the ball 0.5 seconds to reach the other player than its speed relative to the players is 5/0.5 = 10 meters per second, and its speed relative to the ground is (√(5^2 + (0.5(8))^2))/0.5 = 12.8.

## Speed of ball

In what sense is the ball moving at 10 meters per second? "The speed of the ball relative to the ground is actually (10^2+8^2)1/2=12.8 metres per second," and if "it takes 0.4 seconds to travel the 5 metres between the players," then relative to the players the speed is 12.5 meters per second (5/0.4). Also, if the time it takes the ball to reach the other player is 0.4 seconds than its speed relative to the ground is (√(5^2 + (0.4(8))^2))/0.4 = 14.84. However, if it takes the ball 0.5 seconds to reach the other player than its speed relative to the players is 5/0.5 = 10 meters per second, and its speed relative to the ground is (√(5^2 + (0.5(8))^2))/0.5 = 12.8.