MOMENTUM

DEFINITIONS

• Linear momentum (p) is defined as the product of mass (m) and velocity (v):

p = m x v• SI-unit of momentum is 1 kg∙m∙s-1, alternative

unit 1 N∙s can also be used• The change of linear momentum is called the

impulse:

Δp = F x Δt

LAWS OF MOMENTUM

• Newton’s second law states, that the resultant force is proportional to the rate of change of momentum:F=(final momentum – initial momentum)/time taken

F = Δp/Δt

CONSERVATION OF MOMENTUM

• The law of conservation of linear momentum states that the total linear momentum of a system of interacting particles (bodies) remains constant provided there is no resultant external force

COLLISIONS

• Collision in witch no mechanical energy is lost called elastic collision

• If large amount of energy is lost (as heat or/and sound), but the total momentum is still conserved, the collision called totally inelastic collision.

• Inelastic collision, in contrast to an elastic collision, is a collision in which kinetic energy is not conserved.

mA mB

v

mA mB

vv=0

ELASTIC COLLISION (mA=mB)

mA mB

v

mA mB

v/2

TOTALLY INELASTIC COLLISION (mA=mB)

mA mB

v01

mA mB

v2

INELASTIC COLLISION

v1

p01 + p02 = p1 + p2

AND K01 + K02 = K1 + K2

K=1/2mv2 (KINETIC ENERGY)

FORCE ON GRAPH

time/s

Force/N

t1 t2

F

Δp = F x Δt

SAMPLES

Sample No 1

Sample No 2

Sample No 3

Sample No 4

Sample No 5 (1/3)

Sample No 5 (2/3)

Sample No 5 (3/3)