Mech

ENGINEERING MECHANICS (DJJ3053) TITLE : WORK AND ENERGY MEMBER’S NAME:

1. 2. 3. 4.

STUDENT NAME NANDAKUMAAR A/L K.NARENDRAN OGISASFITRI BINTI YASMAN SRI DARSHAN A/L R.SIVADAS MANISHANKER A/L SUPRAMANIAM

MATRIX NUMBER 08DKM15F1335 08DKM15F1308 08DKM15F1306 08DKM15F1327

CLASS: DKM3C LECTURER’S NAME: PN ZETTY ROHAIZA BINTI MOHD SAHAK DATE OF SUBMISSION: 7/10/2016

OBJECTIVE:

 To find the work and energy of a system in the different loads.

APPARATUS: Pulley Set of weight balance String Incline And sliding plane Meter ruler Stopwatch

SAFETY PRECAUTION  Handle the apparatus with care  Do not experiment without supervision lecturer  Make sure incline and sliding plane tight and adjust

Theory The work done by a force on a moving body is defined as the product of the force and the distance moved in the direction of the force. Work also can be define as done by force, F acting on a particle moving along any path is defined as the line integral from position P1 at time t1 to position P2 at time t2

s2

W=

∫ F ds s1

 Work is a scalar  Work is act of force, F along the direction of s  Then W= Fs or W= Fs cos θ  Units are Joules (J) (1 joule = 1 Newton/meter)

The kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes. The same

amount of work is done by the body in decelerating from its current speed to a state of rest. The unit is Joule (J). It is scalar. In formula form: KE =

1 2 2 m v

Relation Between Work And Kinetic Energy

U = KEj – KE1

U= ½ m ( v2 – u2)

Where v = final velocity U = initial velocity

Procedures:

1. Set up the apparatus and material as shown in figure below. 2. Set the distance (s) of first train to second train = _____m. 3. Put the hook with load, 3.1 N and record the time taken when the first coach collides with the second coach. 4. Repeat the experiment with different load value. 5. The value that obtained is recorded 6. The data is than tabulated

Result: Load (N)

Distance , s (m)

3.1 4.1 5.1 6.1

0.62 0.62 0.62 0.62

Angle ( 0 0 0 0

θ °¿

Work, U=Fs cos 1.19 2.54 3.16 3.78

θ

7.1 8.1

Loads

0.62 0.62

0 0

Time (s), time(s), Time(s) , 1st trial 2nd trial average

4.40 5.02

Velocity= distance time( ave)

KE = ½ mv2 = m/s2

(m/s) 3.1

1.32

1.1

1.21

0.51

0.04

4.1

0.93

0.93

0.93

0.67

0.09

5.1

0.68

0.78

0.73

0.85

0.18

6.1

0.63

0.61

0.69

0.91

0.25

7.1

0.63

0.57

0.6

1.03

0.38

8.1

0.32

0.57

0.55

1.13

0.53

Discussion: 1) What are the possible sources of error for the experiment? Give estimates for the percentage errors involved.  Instrument errors. The instrument is not stable. This causes an inaccurate measurement of time T.  Human error. The error may occur when we read the time recorded by the stopwatch because of human reaction time. And it cannot be sure that the ruler is at an exactly perpendicular direction.  Calculation error. When we did the calculation part, we assumed cos θ ≈ θ , which will cause a small error in the result.

2) What is the relation between work and kinetic energy?

The work done on an object by a net force equals the change in kinetic energy of the object: W = KEf - KEi. This relationship is called the work-energy theorem. Proof (for 1. 2.

parallel to

):

W = Fs W = (ma)s (by Newton's second law). From the third equation of motion: as = (v 2 - v02)/2 1/2m(v 2 - v02) = KEf - KEi .

W=

Note:  If the speed of an object increases ( vf > vi )

W > 0.

 If W < 0 then the object is doing work on the agent exerting the net force.  Interpretation of equation, we can think of KE as the work an object can do in coming to rest.

Conclusion: This report has discussed the work and energy of a system in the different load. The objectives of this experiment have been achieved successfully in this formal report. And the experimental results and the analyses have verified and strongly supported our knowledge about the work and energy in the different load. Besides that, the relation between the work and kinetic energy is understood from this experiment that we had carried out. Therefore the skills

and knowledge obtained in this experiment are of great importance in my future engineer courses.

Reference: 1) 2) 3) 4) 5) 6)

http://www.scribd.com http://www.wikipedia.org www.google.com www.yahoo.com Discussion with friends Discussion with lecturer