1. King Fahd University of Petroleum & Minerals
Mechanical Engineering
Dynamics ME 201 BY
Dr. Meyassar N. Al-Haddad
Lecture # 41

2. Conservation of Momentum
Conservation of Linear Momentum
Conservation of Angular Momentum

4. Example 19-7

5. Example 19-7

6. Example 19-7

7. Impact
Impact occurs when two bodies collide with each other during a very short period of time.
Types of impact:
Central impact
Oblique impact
Line of impact
Plane of impact

8. Coefficient of restitution e
Coefficient of restitution e is defined as the ratio of the restitution impulse
To the deformation impulse.
Coefficient of restitution e is defined as the ratio of relative velocity after impact
to the relative velocity before impact
Coefficient of restitution e range between 0-1
Elastic impact e = 1 (re-bounce with same velocity)
Plastic impact e = 0 (couple or stick together and move with common velocity)

9. Procedure for Analysis
Identify the intial velocity “ “you may use”
T1+ V1 = T2+ V2
Apply the conservation of momentum along the line of impact, you will get one equation with two unknown velocity
Use the coefficient of restitution to obtain a second equation
Solve both equation for final velocities after the impact

10. Eccentric Impact
Line of the impact does not coincide with the mass centers of the two bodies
One or both of the bodies are constrained to rotate about a fixed axis
Angular momentum is conserved at point of rotation

11. Procedure for Analysis
Apply the conservation of angular momentum at a rotational point, you will get one equation with two unknown ( v and w )
Use the coefficient of restitution to obtain a second equation O A B

12. Example 19-8
WR=10 Ib
WB=2-Ib
(vB)1= 30 ft/s
wR= ?
e = 0.4

13. Problem 19-40
mp= 7 g
vP= 800 m/s
mD= 5 kg
wD= ?
q = ? stop

14. Problem 19-49
W= 6 Ib
From rest at horizontal
Wbl= 1 Ib
Vbl= 50 ft/s
wrod=?
e= 0.7 1 2

15. Thank you