ENGINEERING MECHANICS
LAB 4 : Law of Collision
LAB 4
MOMENTUM: LAW OF COLLISION
1.0
OBJECTIVE
To verify the conservation of momentum and energy.
2.0
INTRODUCTION AND THEORY
Momentum is defined as the tendency for an object in motion to stay in motion. The
momentum also can be defined as the product of the mass and the velocity of the particle.
Linear momentum is defined as:
P = mv
where,
P = momentum (kgms-1) or Ns
m = Mass (kg)
v = velocity (ms-1)
Velocity ,
v = ∆s
∆t
Where ,
∆s
∆t
= Length of screen = 10 cm = 0.1 m
= Shading time ( given by Time Reader) unit : second
Conservation of Momentum,
Momentum before Collision = Momentum After Collision
P1 + P2 = P’1 + P’2
Elastic Collision
mAvA1 + mBvB1 = mAvA2 +
Inelastic Collision
mAvA1 + mBvB1
=
mBvB2
(mA + mB ) v2
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ENGINEERING MECHANICS
LAB 4 : Law of Collision
Where:
mA
= mass of object 1
mB
= mass of object 2
vA1
= velocity of object 1 before collision
vB1
= velocity of object 2 before collision
vA2
= velocity of object 1 after collision
vB2
= velocity of object 2 after collision
v2
= velocity after collision for both body
Conservation of Kinetic Energy, (KE)
In perfect condition, where e = 1, the conservation of Energy is conserved.
The conservation of Kinetic Energy formula:
Kinetic Energy before Collision (J) = Kinetic Energy after Collision (J)
KE1
+ KE2
=
Elastic Collision
½ mAvA1 2 + ½ mBvB1 2
KE’1
+
KE’2
= ½ mAvA2 2 +
Inelastic Collision
½ mAvA1 2 + ½ mBvB1 2
½ mBvB22
= ½ ( mA + mB ) v2 2
e is coefficient of restitution.
The equation of coefficient of restitution (e) is given by:
e = vB2
vA1
-
vA2
vB1
Coefficient of restitution (e) is equal to 1 means; the collision between the two bodies is
perfectly elastic.
Coefficient of restitution (e) is < 1, means the impact is said to be inelastic. Some energy is
loss during the collision.
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ENGINEERING MECHANICS
3.0
LAB 4 : Law of Collision
EQUIPMENTS / APPARATUS
Figure 3.1 : Apparatus arrangement
Equipments: PHYWE- 1.3.05 Air Track
1. Air Track
11. Magnet w. plug f. starter system
2. Blower
12. End holder
3. Pressure tube
13. Slotted weight
4. Glider f. Air track
14. Light Barrier
5. Tube with Plug
15. Time Reader
6. Needle with plug
16. Portable Balance
7. Fork with plug
17. Barrel Base
8. Rubber bands f. fork w/plug
18. Support Rod
9. Plate with plug
19. Right Angle clamp
10.Starter system
20. Connecting cord, red, yellow, blue
Safety Instruction: The equipments you are using are potentially dangerous. You are
strictly required to follow the procedures outlined below. Do not make any unnecessary
actions which are not stated in the procedure. If not, an accident may occur. In case of
doubt, contact the Technician or Training Engineer immediately.
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ENGINEERING MECHANICS
4.0
LAB 4 : Law of Collision
PROCEDURE
This experiment consists from 2 parts which are:
1)
3)
Part 1 - Elastic Collision
Part 2 – Inelastic Collision
Part 1 - Elastic Collision
In this experiment we will measure the speeds of two air glider before and after they collide
with each other in ‘Elastic Collision’.
No.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Procedure
Plug M1 Glider with rubber band attachment.
Measure and record M1 and M2 Glider weight separately using JADEVER
electronic scale.
Set the ‘Light barrier’ a position 70cm and 140cm to the air track.
Push the ‘Starter’ device.
Switch ‘ON’ Air Blower unit at position at speed No. 5 .
Place M1 Glider on air track and attach it to Starter unit magnet.
Place M2 Glider on air track. Position it at 110 cm on air track. Then hold the M2
Glider.
Switch ‘ON’ the ‘Time Reader’ unit. Push reset button to ensure all readings
become Zero.
Release M1 Glider by pushing the starter release pin at the top of starter unit. At
the same time gently release M2 Glider and ensure Glider M2 is static at position
110 cm on air track.
The M1 glider will hit the M2 glider. Record the time before and after collision.
Record your data in Table 1-A
Repeat the procedure but with additional weight 100g at both wing side of M1
glider. Record your data in Table 1-B
Calculate the :
i.
Velocity
ii.
Momentum
iii.
Kinetic Energy
iv.
Energy Loss
Show all your calculations.
Page 4 of 12
ENGINEERING MECHANICS
LAB 4 : Law of Collision
Part 2 – Inelastic Collision
In this experiment we will measure the speeds of two air glider before and after they collide
with each other in ‘Inelastic Collision.
No.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Procedure
Plug M1 Glider with needle plug attachment.
Measure and record M1 and M2 Glider weight separately using JADEVER
electronic scale.
Set the ‘Light barrier’ a position 70cm and 140cm to the air track.
Push the ‘Starter’ device
Switch ‘ON’ Air Blower unit at position 5 speeds.
Place M1 Glider on air track and attach it to Starter unit magnet.
Hold M2 Glider at position 110 cm on air track.
Switch ‘ON’ the ‘Time Reader’ unit. Push reset button to ensure all readings
become Zero.
Release M1 Glider by pushing the starter release pin at the top of starter unit. At
the same time gently release M2 Glider and ensure Glider M2 is static at position
110 cm on air track.
The M1 glider will hit the M2 glider, and both gliders will move together. Record
the time before and after collision. Record your data in Table 2-A
Repeat the procedure but with additional weight 100g at both wing side of M1
glider. Record your data in Table 2-B
Calculate the :
v.
Velocity
vi.
Momentum
vii.
Kinetic Energy
viii.
Energy Loss
Show all your calculations.
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ENGINEERING MECHANICS
5.0
LAB 4 : Law of Collision
RESULTS
Part 1 - Elastic Collision
Part 1 : Weight added to both M1 wing:
Glider
Mass
(kg)
0
g
Before Collision
Time (s)
Velocity (m/s)
After Collision
Time (s)
Velocity (m/s)
M1
M2
Momentum Before Collision
Calculation :
Momentum After collision
Calculation :
Total
Total
=
=
Coefficient of Restitution, e
Calculation :
e = _________
Kinetics Energy Before Collision
Calculation :
Kinetics Energy After Collision
Calculation :
Total
Total
=
=
Kinetic Energy Loss
Calculation :
Total Energy Loss :
Table 1-A
Page 6 of 12
ENGINEERING MECHANICS
LAB 4 : Law of Collision
Part 1 : Weight added to both M1 wing:
Glider
Mass
(kg)
100
g
Before Collision
Time (s)
Velocity (m/s)
After Collision
Time (s)
Velocity (m/s)
M1
M2
Momentum Before Collision
Calculation :
Momentum After collision
Calculation :
Total
Total
=
=
Coefficient of Restitution, e
Calculation :
e = _________
Kinetics Energy Before Collision
Calculation :
Kinetics Energy After Collision
Calculation :
Total
Total
=
=
Kinetic Energy Loss
Calculation :
Total Energy Loss :
Table 1-B
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ENGINEERING MECHANICS
LAB 4 : Law of Collision
Part 2 – Inelastic Collision
Part 2 : Weight added to both M1 wing:
Glider
Mass
(kg)
0
g
Before Collision
Time (s)
Velocity (m/s)
After Collision
Time (s)
Velocity (m/s)
M1
M2
Momentum Before Collision
Calculation :
Momentum After collision
Calculation :
Total
Total
=
=
Coefficient of Restitution, e
Calculation :
e = _________
Kinetics Energy Before Collision
Calculation :
Kinetics Energy After Collision
Calculation :
Total
Total
=
=
Kinetic Energy Loss
Calculation :
Total Energy Loss :
Table 2-A
Page 8 of 12
ENGINEERING MECHANICS
LAB 4 : Law of Collision
Part 2 : Weight added to both M1 wing:
Glider
Mass
(kg)
100
g
Before Collision
Time (s)
Velocity (m/s)
After Collision
Time (s)
Velocity (m/s)
M1
M2
Momentum Before Collision
Calculation :
Momentum After collision
Calculation :
Total
Total
=
=
Coefficient of Restitution, e
Calculation :
e = _________
Kinetics Energy Before Collision
Calculation :
Kinetics Energy After Collision
Calculation :
Total
Total
=
=
Kinetic Energy Loss
Calculation :
Total Energy Loss :
Table 2-B
Page 9 of 12
ENGINEERING MECHANICS
6.0
LAB 4 : Law of Collision
QUESTIONS
6.1
For each part, is the total momentum before and after all collisions same?
Explain your findings.
6.2
Is the total kinetic energy before and after collision same for each parts?
Explain your findings.
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ENGINEERING MECHANICS
LAB 4 : Law of Collision
6.3
What is Elastic and Inelastic collision? Explain with your own words.
6.4
If mass and velocity of glider increased what will happen to the kinetics
energy? Explain your findings.
6.5
During the collision, some kinetic energy are ‘loss’. In your opinion, what is
the term ‘loss’ is referred?. Explain your findings.
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ENGINEERING MECHANICS
7.0
LAB 4 : Law of Collision
DISCUSSIONS
Describe what have you observed and understand during conducting experiment.
Comment about the results, and also give your reason and opinion to this experiment.
8.0
CONCLUSION
Comment about the experiment objective.
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