Kinematics
A machine is a device that accepts energy in some available form and utilizes it to do a type of work. Energy, work, or power has to be transferred from one mechanical part to another to run a machine. While the transfer of energy between two machine parts, those two parts experience a relative motion with each other. Studying such relative motions is termed kinematics.
Kinetic Energy and Work-Energy Theorem
In physics, work is the product of the net force in direction of the displacement and the magnitude of this displacement or it can also be defined as the energy transfer of an object when it is moved for a distance due to the forces acting on it in the direction of displacement and perpendicular to the displacement which is called the normal force. Energy is the capacity of any object doing work. The SI unit of work is joule and energy is Joule. This principle follows the second law of Newton's law of motion where the net force causes the acceleration of an object. The force of gravity which is downward force and the normal force acting on an object which is perpendicular to the object are equal in magnitude but opposite to the direction, so while determining the net force, these two components cancel out. The net force is the horizontal component of the force and in our explanation, we consider everything as frictionless surface since friction should also be calculated while called the work-energy component of the object. The two most basics of energy classification are potential energy and kinetic energy. There are various kinds of kinetic energy like chemical, mechanical, thermal, nuclear, electrical, radiant energy, and so on. The work is done when there is a change in energy and it mainly depends on the application of force and movement of the object. Let us say how much work is needed to lift a 5kg ball 5m high. Work is mathematically represented as Force ×Displacement. So it will be 5kg times the gravitational constant on earth and the distance moved by the object. Wnet=Fnet times Displacement.
OBJECTIVE:
- Determine how physical work is related to the time to walk and hurry up a flight of stairs
- Determine how weight is related to physical work
- Determine how power is related to physical work
- Determine how time is related to power.
INSTRUCTIONS:
- Measure the vertical distance from the ground floor to the landing and from the landing to the 1st floor as shown below (convert to feet). Record this value on the data sheet, column B. Note: Your stairs might not have a landing – that’s ok. Just measure the vertical height from the bottom to the top of the stairs.
- Record your weight (pounds) in column A of the data sheet. Multiply column A and column B. Record this value in column C.
- Measure the time it takes to walk (at a normal pace) up the stairs from the ground floor to the first floor – use the hand rail for support. Measure 3 times and calculate the average time. Record these values in column D.
- Measure the time it takes to briskly walk (not run) up the stairs from the ground floor to the 1st floor – use the hand rail for support. Measure 3 times and calculate the average time. Record these values in column E.
- Calculate the power it took to walk and to hurry from the ground floor to the 1st floor. Enter your calculation in column F and G respectively.
- Answer the questions.
- Email your exercise to the instructor.
Data Table for Stairs/Work/Power Exercise
|
A |
B |
C |
D |
E |
F |
G |
|
Weight (lb) |
Vertical Height (ft) |
Work Done (ft*lbs) |
Time Walk (sec) |
Time Hurry (sec) |
Power Calculation Walk (hp) |
Power Calculation Hurry (hp) |
|
132lbs |
5.2ft |
686.4 |
20 |
6.50 |
|
|
|
|
|
|
21 |
6.40 |
|
|
|
|
|
|
21 |
6.50 |
|
|
|
|
|
Avg Time |
20.33 |
6.46sec |
|
|
CALCULATIONS:
Power = Work/Time Conversion: 1 ft*lb/s = 0.00182 horsepower
Walk:
Hurry:
QUESTIONS:
- How is work related to the time to walk and hurry up the stairs?
- What part does weight play in the exercise?
- Do you do more work if you are heavier?
- Do you exert more power if you are heavier?
- How is time related to power?
ANSWERS
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