You are in the bleachers at the World Series and a game winning baseball (mass 0.15 kg) approaches at 28 m/s. You want to catch it, but you don't want to hurt your had since that might impede your ability to do physics homework. To lessen the impact you slow it down with your hand over a displacement of 0.8 m as you catch it. What external work must you do on the baseball in J?

Question

Physics

Raul

16 December, 12:06

You are in the bleachers at the World Series and a game winning baseball (mass 0.15 kg) approaches at 28 m/s. You want to catch it, but you don't want to hurt your had since that might impede your ability to do physics homework. To lessen the impact you slow it down with your hand over a displacement of 0.8 m as you catch it. What external work must you do on the baseball in J?

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Siena Khan · Answer 1

58.8 Joules work must be done

Explanation:

Equations of motion related distance, velocity and acceleration:

v² - v₀² = 2 x acc x Δdistance

so acc = (0 - 28²) / (2 x 0.8 m) = - 490 m/s² (negative acceleration means deceleration)

Ave force F to decelerate mass 0.15 kg = m x a = 0.15 x 490 = 73.5 Newtons

Work done W = Force x distance = 73.5 N x 0.8 m = 58.8 Nm (i. e. Joules)