Stair Lab Post Lab Questions
Purpose
• To determine the work and power required to climb one floor stairs.
• To determine the energy burned during that exercise
Curriculum
We examined three physical quantities: Force, Work, and Power and related units of measure. Newtons, Joules, Watts, and soon to come… calories.
One of the most important concepts in science is energy. Our universe is made of matter and energy. Matter is substance and energy moves the substance. The concept of matter is easy to comprehend, because we can see, feel, smell, or measure it. Energy, on the other hand is very abstract concept, we can’t see, feel, or smell it. But fortunately we can measure it. There are a number of units used to measure energy. A non metric unit of calorie (cal) is one of them. The energy equal to 1 calorie is defined as the amount of heat required to raise the temperature of one gram of water from 14.5oC to 15.5oC. When we work with nutritional values and food, a unit of Calories (Cal - capitol C) is used. Relation between cal and Cal is:
1 Cal = 1000 cal
Metric unit for energy is Joule (J). The energy of 1 Joule is equal to amount of heat needed to rise the temperature of 1 g of water for 1 oC. The relation between the three mentioned units is:
1 Cal = 1000 cal
1 cal = 4.19 J
1 Cal = 4190 J
When we lift the load against the earth’s gravity, work is done on the mass. The more mass on the load or the higher we lift the load, the more work is done. Every time when force is applied and something has moved because of that force, some work is done. Work is defined a as product of force and distance.
W = F d
If we lift 20 kg one story up, we perform twice as much work compared to lifting only 10 kg load, because twice as much force is needed to lift 20 kg. The unit of measurement of work is combination of unit of force N and unit of distance m: Nm which is also called Joule J.
Work can be done at various rates, or energy can be changed at various rates. In some situations happens faster in some others it happened slower. You can walk up stairs or you can run upstairs in one floor. In both cases you are doing same work but at different rates. The rate at which the energy is changed, or work is done is called Power P. P = work done/ time interval. The unit of power is: Joule/second = Watt (J/s = W)
Post Lab Questions
1.) Two people of the same mass climb the same flight of stairs. Myles climbs the stairs in 25 seconds. Ann person takes 35 seconds. Which person does the most work? Which person expends the most power? Explain your answers.
2.) A box that weighs 1000 Newtons is lifted a distance of 20.0 meters straight up by a rope and pulley system. The work is done in 10.0 seconds. What is the power developed in watts and kilowatts?
3.) A person of mass 64 kg climbs up a ladder to a height of 5.0 meters.
a.) What work does the person do?
b.) What is the increase in the gravitational potential energy of the person at this height?
c.) Where does the energy come from to cause this increase in P.E. (Potential Energy).
4. Which requires more work: lifting a 50 kg box vertically for distance of 2 m, or lifting a 25 kg box vertically for a distance of 4 meters?
Which requires more work: lifting a 50 kg box vertically for distance of 2 m, or lifting a 25 kg box vertically for a distance of 4 meters.
