1. King Fahd University of Petroleum & Minerals
Mechanical Engineering
Dynamics ME 201 BY
Dr. Meyassar N. Al-Haddad
Lecture # 18

2. Kinetics of a Particle: Impulse and Momentum
Objective:
To develop the principle of linear impulse and momentum for a particle. To solve problems involving force, time, and velocity.

3. Newton’s Second Law Impulse change in momentum
Principle of linear impulse and momentum equation

4. Linear momentum L = mv Measure of impact effect
Compare
bullets with small mass and high velocity
Ship with huge mass and slow velocity
L is a vector -- points in same direction as v
Unit: kg.m/s or slug.ft/s
Components (rectangular coordinates):
Lx=mvx, Ly=mvy, Lz=mvz

5. Linear Impulse Measure the effect of force during the time force acts.
I is a vector quantity in the direction of force
Unit N.s or Ib.s
When F is constant

6. Principle of Linear Impulse and Momentum
Initial momentum Sum of all Impulse = Final momentum

7. Principle of Linear Impulse and Momentum for a system of Particles

8. Scalar Equations

9. Free Body Diagram Select the particle Establish x, y frame
Establish the direction of the particle initial and final velocities
Drew the impulse and moment diagrams. Include all the forces acting on the particle’s FBD will create an impulse, even though some of these forces will do no work.
Resolving the vectors along the x, y axis
Apply

10. Example 15-1
m=100 kg
At rest smooth
t=10 s
V2=?
N=?

11. Example 15-3
W=50 Ib
P=(20t) Ib
V2=?
T=2 sec.
V1=3 ft/s
mk=0.3

12. Example 15-3
From rest
vB=?
t=6 sec.
Block A
Block B

13. Problem 15-4
m=12 Mg
Fy=150 kN
V=?
h=?
t=6 s
Start from rest

14. Problem 15-6
m = 28 Mg
At rest
V = ?
t = 4 s
F = t2

15. Problem 15-19
m = 75 kg
Start from rest
v = 200 mm/s
t = 0.4 s.
mk= 0.5
Impulse = ?

16. Thank You