Kinematics And Dynamics

INSTITUT PENDIDIKAN GURU MALAYSIA KAMPUS SULTAN MIZAN, 22200 BESUT, TERENGGANU DARUL IMAN. PPISMP SEMESTER 1 PHYSIC REPORT PRACTICAL SCIENCE 2 EXPERIMENT 3

NAME

:

SITI QURRATUL AINI ULFA BINTI RODIN JAYA

I/C NO

:

910606-03-6028

COURSE

:

SCIENCE

SUBJECT

:

SCIENCE (PHYSIC)

TOPIC

:

KINEMATICS AND DYNAMICS

SUPERVISOR

:

EN.ROSDI BIN OMAR

SEMESTER 1 Practical Science 2

Experiment 3 Topic

:

Kinematics and Dynamics

Purpose

:

To verify the principle of conversation of linear momentum for a collision of two bodies of equal mass.

Theory

:

Figure 1 below shows the bob of the pendulum being released from P to Q.

If v is the velocity of the bob at Q and m is the mass of the bob, then, mgh = 12mv2…………(1) If

z = horizontal displacement of bob from Q L = length of pendulum

and

θ = angular displacement of the bob, then h =L(1-kos θ) =L(2sin2θ2)

For θ smaller than 15°, sin2 θ2 =(θ2)2 ;z=Lθ Then,

h=12 Lθ2=12z2L

From equation (1),v2=2gh, Then

v2=z2gL and kinetic energy Ek=12mv2=mgz22L

∴v∝z and kinetic energy Ekccz2

Apparatus

:

(I)

Hooking plank

(II)

Two bobs equal mass

(III)

Two threads of length about 2 m

(IV)

Two retort stands and clamps

(V)

A metal wire as indicator

(VI)

A screen to act as marker to the distance of collision

(VII)

A meter rule

(VIII) Plasticine (IX)

A pair of vernier calipers

(X)

Blocks for raising the height of the retort stands

Procedure

:

(a) Set up the apparatus as shown in Figure 2.

(b) Using a pair of vernier calipers, measure the diameter of the pendulum bob. (c) Hook the pendulum bob on the hooking plank as shown in the diagram above and make sure that the center of the two pendulum bobs rest at the same level and not less than 80 cm from the hooking plank. (d) Place a meter rule below the bobs. Adjust the meter rule so that the 50 cm mark is just below the point of contact of the bobs. (e) Move one of the bobs away, and determine the position of the centre of other bob and record corresponding reading on the meter rule as X01. Repeat the process, and record the position of the centre of the other bob as X02. (f) Displace one of the bobs about 20 cm away. Record the position of the centre of the bob as X1. Release the bob so as to make direct head-on collision with the other bob (The first bob should be almost at rest after the head-collision). (g) If it is a head-on collision, record the position of the screen that serves as a marker for the distance of collision. Repeat the process if the collision is not the head-on collision. (h) Record the position of the centre of the second bob, X2, if the collision is a headon collision. (i) Repeat steps (e) through (g) for displacements between 20 cm to 10 cm.

(j) Record all your readings and tabulate X1, Z1=X1-X01, (Z)2, X2, Z2=X2-X02, (Z2)2, and (Z2Z1)2 (k) Stick a small lump of plasticine on one of the pendulum bobs and repeat steps (e) through (g). After the collision, both the pendulum bobs move as one body. (l) Record all your readings, and tabulate X'1, Z'1=X'1-X'01, (Z')2, X'2, Z'2=X'2-X'02, (Z'2)2, and (Z'2Z'1)2. (m)From the results obtained, deduce a conclusion on the momentum and kinetic energy of the two systems. State whether the collisions in the first and second systems are elastic or not.

Results

:

a) Result without plasticine(Elastic collision) X1 20.0 18.0

Z1=(X1-X01) 19.4 17.4

(Z1)2 376.36 302.76

X2 18.3 17.6

Z2=(X2-X02) 17.7 17.0

(Z2)2 313.29 289.00

(Z2/Z1)2 0.832 0.955

16.0 14.0 12.0 10.0

15.4 13.4 11.4 9.4

237.16 179.56 129.96 88.36

15.7 13.6 11.9 9.8

15.1 13.0 11.3 9.2

228.01 169.00 127.69 84.64

0.961 0.941 0.983 0.958

Z’2=(X’2-X’02) 11.0 10.1 9.2 8.3 6.7 5.5

(Z’2)2 121.00 102.01 84.64 68.89 44.89 30.25

(Z’2/Z’1)2 0.915 0.908 0.900 0.890 0.866 0.840

b) Result with plasticine(Inelastic collision) X’1 20.0 18.0 16.0 14.0 12.0 10.0

Z’1=(X’1-X’01) 11.5 10.6 9.7 8.8 7.2 6.0

Discussion

(Z’1)2 132.25 112.36 94.09 77.44 51.84 36.00

X’2 11.5 10.6 9.7 8.8 7.2 6.0

:

1) Kinetic energy and momentum are conserved in the collision between two bobs without plasticine because the ratio of kinetic energy and momentum before collision to kinetic energy and momentum after collision is 0.94 which is near to 1.0. 2) This show the kinetic energy and momentum before collision is same as kinetic energy and momentum after collision. 3) Kinetic energy and momentum are not conserved in the collision between two bobs with plasticine because the ratio of kinetic energy and momentum before collision to kinetic energy and momentum after collision is 0.39 which is far to 1.0.

4) This show the kinetic energy and momentum before collision is not same as kinetic energy and momentum after collision. 5) Precaution

:

a. When doing this experiment, the fans should be switch off during the experiment to minimize the air resistance to the collision. b. The external force should not be acted on the pendulum to make sure the pendulum bob oscilate with its natural frequency to get more accurate result. Conclusion

:

Kinetic energy and momentum are conserved in elastic collision but not conserved in inelastic collision.