A \(62-\mathrm{kg}\) woman takes \(6.0 \mathrm{s}\) to run up a flight of stairs. The landing at the top of the stairs is \(5.0 \mathrm{m}\) above her starting place. (a) What is the woman's average power output while she is running? (b) Would that be equal to her average power input-the rate at which chemical energy in food or stored fat is used? Why or why not?

Short Answer

Expert verified
Answer: The woman's average power output while running up the stairs is 507 W. This is not equal to her average power input, as some of her body's stored energy is lost as heat and used for other purposes.

Step by step solution

01

Calculate the work done by the woman while running up the stairs

First, we will find the gravitational potential energy gained by the woman as she climbs the stairs. We can find this using the formula: \(PE = m \cdot g \cdot h\) where \(PE\) is the potential energy, \(m\) is her mass, \(g\) is gravitational acceleration (\(9.8 \, m/s^2\)), and \(h\) is the height of the stairs. Plugging in the given values: \(PE = 62 \, kg * 9.8 \, m/s^2 * 5.0 \, m\)
02

Calculate the gravitational potential energy

Now we can calculate the gravitational potential energy: \(PE = 62 \, kg * 9.8 \, m/s^2 * 5.0 \, m = 3042 \, J\) (joules)
03

Calculate the average power output

Now that we have the work done (potential energy gained), we can find the average power output by dividing it by the time taken: \(P_\text{out} = \frac{PE}{t}\) \(P_\text{out} = \frac{3042 \, J}{6.0 \, s}\)
04

Solve for average power output

Now we can solve for average power output: \(P_\text{out} = \frac{3042 \, J}{6.0 \, s} = 507 W\)
05

Average power input

Now let's discuss the average power input. The woman's body uses chemical energy stored in the form of food or fat. The average power output represents the rate at which this energy is converted into work to climb the stairs. However, not all of the energy stored in the body is used for this purpose - some energy is lost as heat, and some might be used for other bodily activities. Therefore, we can conclude that the average power input will be higher than the average power output found in Step 4. To summarize: - (a) The woman's average power output while running up the stairs is 507 W. - (b) That would not be equal to her average power input, as some of her body's stored energy is lost as heat and used for other purposes.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

An ideal spring has a spring constant \(k=20.0 \mathrm{N} / \mathrm{m}\) What is the amount of work that must be done to stretch the spring \(0.40 \mathrm{m}\) from its relaxed length?
How much work must Denise do to drag her basket of laundry of mass $5.0 \mathrm{kg}\( a distance of \)5.0 \mathrm{m}$ along a floor, if the force she exerts is a constant \(30.0 \mathrm{N}\) at an angle of \(60.0^{\circ}\) with the horizontal?
A block (mass \(m\) ) hangs from a spring (spring constant k). The block is released from rest a distance \(d\) above its equilibrium position. (a) What is the speed of the block as it passes through the equilibrium point? (b) What is the maximum distance below the equilibrium point that the block will reach?
A \(1500-\mathrm{kg}\) car coasts in neutral down a \(2.0^{\circ}\) hill. The car attains a terminal speed of \(20.0 \mathrm{m} / \mathrm{s} .\) (a) How much power must the engine deliver to drive the car on a level road at $20.0 \mathrm{m} / \mathrm{s} ?$ (b) If the maximum useful power that can be delivered by the engine is \(40.0 \mathrm{kW},\) what is the steepest hill the car can climb at \(20.0 \mathrm{m} / \mathrm{s} ?\)
(a) If the length of the Achilles tendon increases \(0.50 \mathrm{cm}\) when the force exerted on it by the muscle increases from \(3200 \mathrm{N}\) to $4800 \mathrm{N},$ what is the "spring constant" of the tendon? (b) How much work is done by the muscle in stretching the tendon \(0.50 \mathrm{cm}\) as the force increases from \(3200 \mathrm{N}\) to \(4800 \mathrm{N} ?\)
See all solutions

Recommended explanations on Physics Textbooks

View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free