<<

„ In order to change the of an object, a must be applied

Momentum „ The rate of change of momentum of an object is equal to the „ The linear momentum of an object of acting on it m moving with a is defined as the product of the mass and the velocity „ Gives an alternative statement of ’s law

„

„ SI Units are kg m / s p „ Vector quantity, the direction of the momentum is the same as the velocity’s

t

Impulse Average Force in

„ When a single, constant force „ The average force acts on the object, there is an can be thought of as impulse delivered to the object the constant force r r r that would give the „ I = ∆p = F∆t r same impulse to the „ I is defined as the impulse object in the time „ Vector quantity, the direction is the interval as the actual same as the direction of the force time-varying force gives in the interval r r r I = ∆p = Fav∆t

Impulse-Momentum Where does it show up? Theorem

„ The theorem states that the impulse acting on the object is equal to the change in momentum of the object r „ I = for a

constant force If ∆p is constant, increasing ∆t will reduce Fav

„ If the force is not constant, use the and vice versa average force applied r r r I = ∆p = Fav∆t

1 Deliberately increasing

∆t to reduce Fav

Large Fav, Small ∆t

Conservation of Conservation of Momentum Momentum, cont

„ Momentum in an isolated system in „ The principle of conservation of which a occurs is conserved momentum states when no „ A collision may be the result of physical external act on a system contact between two objects consisting of two objects that „ “Contact” may also arise from the collide with each other, the total electrostatic of the in momentum of the system remains the surface of the bodies constant in time „ An isolated system will have not external forces „ Specifically, the total momentum before the collision will equal the total momentum after the collision

Conservation of Momentum, cont.

„ Mathematically:

„ Momentum is conserved for the system of objects

„ Assumes only internal forces are acting during the collision

„ Can be generalized to any number of objects

2