Reporting Category: Motion and Forces Standard: 2.4 - Describe both qualitatively and quantitatively the concept of power as work done per unit time

A 50 kg student climbs 3 m to the top of a set of stairs.

Calculate the change in the studentâ€™s gravitational potential energy from the bottom to the top of the stairs. Show your calculations and include units in your answer.

How much total work does the student do while climbing the stairs? Show your calculations or explain your reasoning. Include units in your answer.

It takes the student 30 s to climb to the top of the stairs.

What is the average power generated by the student climbing the stairs? Show your calculations and include units in your answer.

The next day the student carries a 10 kg backpack up the same stairs and again takes 30 s to reach the top of the stairs.

Is the average power you calculated in part (c) greater than, less than, or equal to the average power the student generated the next day? Explain your answer.

Scoring Guide and Sample Student Work Select a score point in the table below to view the sample student response.

The response demonstrates a thorough understanding of how work can be expressed as a change in mechanical energy and of the relationship between work and power. The response correctly calculates the change in the studentâ€™s gravitational potential energy, the amount of work the student performs, and the average power of the student. The response correctly compares the power of the student climbing the stairs with and without the backpack.

The response demonstrates a general understanding of how work can be expressed as a change in mechanical energy and of the relationship between work and power.

The response demonstrates a limited understanding of how work can be expressed as a change in mechanical energy and of the relationship between work and power.

The response demonstrates a minimal understanding of how work can be expressed as a change in mechanical energy and of the relationship between work and power.