Chapter 9: Q.60 (page 230)

A $90 k g$ firefighter needs to climb the stairs of a $20 m$ -tall building while carrying a $40 k g$ backpack filled with gear. How much power does he need to reach the top in $55 s$ ?

Short Answer

Expert verified

The power need to reach the top in $55 s$ is $460 W$

Step by step solution

Content Introduction

Power is the rate of doing work. It is calculated as

$P = \frac{W}{t}$

Work done is the dot product of force and displacement.

$W_{(\vec{F})} = \vec{F} . \vec{d} W_{(\vec{F})} = F d \cos (θ)$

Substitute $m g f o r F_{g}$ and $180 °$ for $θ$ .

$W_{(\vec{F})} = m g d (\cos (180 °)) W_{(\vec{F})} = - m g d$

Hence, work done by firefighter is equal to negative of potential energy.

Content Explanation

The power need to reach the top in $55 s$ is

$P = \frac{m g d}{t} P = \frac{(130 k g) (9.8 m / s) (20 m)}{55 s} P = 460 W$

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A $90 k g$ firefighter needs to climb the stairs of a $20 m$ -tall building while carrying a $40 k g$ backpack filled with gear. How much power does he need to reach the top in $55 s$ ?

Short Answer

Step by step solution

Content Introduction

Content Explanation

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A 90kg firefighter needs to climb the stairs of a 20m-tall building while carrying a 40kg backpack filled with gear. How much power does he need to reach the top in 55s?

Short Answer

Step by step solution

Content Introduction

Content Explanation

One App. One Place for Learning.

Most popular questions from this chapter

Recommended explanations on Physics Textbooks

Space Physics

Engineering Physics

Electricity and Magnetism

Fundamentals of Physics

Measurements

Waves Physics

Study anywhere. Anytime. Across all devices.

A $90 k g$ firefighter needs to climb the stairs of a $20 m$ -tall building while carrying a $40 k g$ backpack filled with gear. How much power does he need to reach the top in $55 s$ ?