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Ch. 08 - Conservation of Energy
Giancoli Douglas - Physics for Scientists and Engineers 5th edition
Giancoli Douglas5th editionPhysics for Scientists and EngineersISBN: 9780137488179Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoGiancoli Douglas 5th editionCh. 08 - Conservation of EnergyProblema 57b
Capitolo 8, Problema 57b

An 85-kg football player traveling 5.0 m/s is stopped in 1.0 s by a tackler. What average power is required to stop him?

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Determine the initial kinetic energy of the football player using the formula for kinetic energy: Ki = (1/2)mv2, where m is the mass (85 kg) and v is the velocity (5.0 m/s).
Since the player is stopped, the final kinetic energy is zero. The change in kinetic energy is equal to the initial kinetic energy: ΔK = Ki - Kf, where Kf = 0.
The work done to stop the player is equal to the change in kinetic energy: W = ΔK. Substitute the value of ΔK from the previous step.
The average power required to stop the player is given by the formula: P = W/t, where t is the time interval (1.0 s). Substitute the value of W from the previous step.
Simplify the expression to find the average power. Ensure all units are consistent (mass in kg, velocity in m/s, time in seconds) to get the power in watts (W).

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Momentum

Momentum is the product of an object's mass and its velocity, represented by the equation p = mv. In this scenario, the football player's momentum before being tackled can be calculated using his mass (85 kg) and his speed (5.0 m/s). Understanding momentum is crucial for analyzing the changes in motion and the forces involved in stopping the player.
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Intro to Momentum

Impulse

Impulse is defined as the change in momentum of an object when a force is applied over a period of time. It can be calculated using the formula Impulse = Force × Time. In this case, the tackler applies a force over 1.0 second to stop the player, and calculating the impulse will help determine the average force exerted during the tackle.
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Impulse & Impulse-Momentum Theorem

Power

Power is the rate at which work is done or energy is transferred, expressed as Power = Work / Time. In this context, the work done to stop the football player can be related to the impulse and the time taken (1.0 s). Calculating the average power required to stop the player involves determining the work done in stopping him and dividing it by the time interval.
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Power
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