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Kinetics of Particles Impulse Momentum Method
INTRODUCTION Having studied in the earlier chapters two different approaches, we shall in this chapter learn the third approach to the solution of kinetics of particles. This approach requires the use of Impulse Momentum Equation involving the parameters like force, mass, velocity and time. Using this equation eliminates the determination of acceleration giving direct results in most of the cases. In the second part of this chapter we shall deduce the Conservation of Momentum Equation from the basic Impulse Momentum Equation and use it to solve problems involving a system of particles subject to internal action and reaction forces and not involving any external forces on the system (i.e. such a system where momentum is conserved). Study of collision of particles forms the third part of this chapter. Here we shall learn the interesting phenomenon which takes place during a collision. The study reveals that there exists a certain relation between the velocities of the colliding particles before they collide to the velocities they acquire after impact. IMPULSE Consider a particle acted upon by a force F as shown in Fig. (a), for a duration of t sec.
This force is said to impart an impulse on the particle and the magnitude of this impulse is the product of the force and the duration for which it acts. If the force F is constant (Fig. (b)), during the time it acts, then Impulse = F t …………[1(a)] If the force F is variable (Fig. (c)), the impulse between the time interval t1 and t2 is t2
Impulse = Fdt
…………[1(b)]
t1
Impulse is a vector quantity and its unit is N.s
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